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  • Articles  (144)
  • nitrogen  (144)
  • Springer  (144)
  • American Meteorological Society
  • 1995-1999  (144)
  • 1990-1994
  • 1999  (75)
  • 1996  (69)
  • 1
    Electronic Resource
    Electronic Resource
    The effect of nitrogen fertilizer applied to Euphorbia pulcherrima on the parasitization of Bemisia argentifolii by the parasitoid Encarsia formosa (1996)
    Springer
    Entomologia experimentalis et applicata 78 (1996), S. 105-110 
    Details
    ISSN: 1570-7458
    Keywords: Bemisia argentifolii ; Encarsia formosa ; poinsettia ; parasitoids ; nitrogen ; tri-trophic level interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract More wasps of Encarsia formosa Gahan (Hymenoptera: Aphelinidae) were found on fertilized poinsettias, Euphorbia pulcherrima (Willd.) (Euphorbiaceae), than on non-fertilized plants. Parasitization of Bemisia argentifolii Bellows & Perring (Homoptera: Aleyrodidae) by E. formosa was higher on plants treated with calcium nitrate than with ammonium nitrate or on control plants. In a no-choice test, host feeding by E. formosa was higher when hosts were on fertilized plants than when hosts were on control plants. The nitrogen content of whitefly pupae reared on plants treated with ammonium nitrate was higher than those on calcium nitrate-treated plants. Variability in the parasitization of B. argentifolii by E. formosa appears to be due to host plant-mediated differences in the whiteflies. E. formosa may be influenced by the nutritional suitability of the host, which influences whether wasps continue to oviposit, feed, or disperse.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00304461
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  • 2
    Electronic Resource
    Electronic Resource
    Compensatory responses of Samea multiplicalis larvae when fed leaves of different fertilization levels of the aquatic weed Pistia stratiotes (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 205-216 
    Details
    ISSN: 1570-7458
    Keywords: Samea multiplicalis ; Spodoptera pectinicornis ; Pistia stratiotes ; waterlettuce ; nitrogen utilization efficiency ; compensatory feeding ; nitrogen ; biological control of weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Compensatory responses of caterpillars fed low quality food include increased consumption and utilization of essential nutrients. Information about an insect's responses to nutritional challenges from their host plants could benefit weed biological control efforts in the selection and establishment of new agents. The target weed, Pistia stratiotes L. (Araceae) is a floating aquatic plant that has relatively low nitrogen levels which are further diluted with high water content. Efforts to establish the insect Spodoptera pectinicornis (Hampson) (Lepidoptera: Noctuidae) for biological control of P. stratiotes could benefit by examining the nutritional responses of a similar widely established lepidopteran species, Samea multiplicalis (Guenèe) (Lepidoptera: Pyralidae). Larvae of this species were fed leaves of P. stratiotes plants that had been fertilized (NPK) at high and low rates. The leaves of the fertilized plants had a 4.3-fold increase in nitrogen (dry weight) and a 1.6-fold increase in water content. The results suggest that no compensatory increases occurred in larvae fed leaves from the low fertilized plants as no changes were found in fresh mass consumption or nitrogen utilization efficiency. Consequently, development time from second-third instars to pupation was delayed about 3 days compared with larvae fed the high nitrogen leaves. Furthermore, consumption of nitrogen was only 30% and its accumulation into larval tissues was only 60% compared with the larvae fed the high fertilized leaves. The resulting larvae had both a final biomass and a growth rate that were reduced by 40%. Regardless of plant fertilizer level, the larvae fed at a rate 5–10 times greater than that of similar lepidopteran species consuming either low or high quality diets, suggesting that the S. multiplicalis larvae may be functioning at their biological limit for ingesting food.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003771512722
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  • 3
    Electronic Resource
    Electronic Resource
    Plant quality or quantity? Host exploitation strategies in three Chrysomelidae species associated with Asteraceae host plants (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 165-177 
    Details
    ISSN: 1570-7458
    Keywords: Chrysomelidae ; herbivory ; Asteraceae ; life history ; nitrogen ; plant quality ; season
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytophagous insects which feed on the leaves of herbaceous host plants have to adapt their life histories to the fact that protein nitrogen is usually highest in growing tissues in spring. We monitored field populations of larvae and adults of three chrysomelid species (Galeruca tanaceti (L.) (main host Achillea millefolium (L.) Yarrow), Cassida rubiginosa (Mueller) (main host Cirsium arvense (L.) Scop.) and Oreina luctuosa (Suffrian) (host Centaurea scabiosa (L.)) together with the amount of protein nitrogen of their food resources and host plant biomass. As expected, the development of host quality, measured as concentration of protein nitrogen, and host plant biomass showed inverse trends during the season. The euryphagous G. tanaceti attacks Achillea early and profits from high nitrogen concentrations in the leaves. Occasional overexploitations of local populations of Achillea are compensated by the capacity to move to other host species. In C. rubiginosa, a species with a host range restricted to the Cardueae, the main larval feeding activity is postponed to a period when the nitrogen content of the host leaves had dropped to 50% of its initial value, but when host plant biomass had increased by 30%. In the monophagous O. luctuosa the larval development is synchronized with a still later phase of host phenology, at which the nitrogen content is below 50% but plant biomass has reached its maximum. There seem to be selection factors, which oppose the use of high quality food in spring and which force the latter two species to postpone their larval development to a later time in the year. This could be caused by numerous factors like, for example, mean daytime temperature. Later in the season the larvae have to cope with the low quality of their host plants. They have, however, the advantage of large quantities of food available. A laboratory study with adults and mature larvae of O. luctuosa shows that this species can overcome low levels of protein nitrogen either by selecting younger leaves with higher nitrogen concentrations or by increasing the daily food consumption rate (RCR) on leaves with a low level of nitrogen and by a prolongation of the feeding period. In this way the larvae compensate the effect of lower daily growth rates (RGR) and a lower food conversion index (ECI) on poor food quality: Regardless of the level of protein nitrogen there was no statistically significant difference in total gain of weight during the third-instar feeding period and in the weight at the end of the third larval stage. The three investigated chrysomelids show that there exists a broad spectrum of adaptations to overcome the dilemma of variable food quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003709622409
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  • 4
    Electronic Resource
    Electronic Resource
    Simulation of kinetics of nitrogen desorption from Rh(111) (1996)
    Springer
    Catalysis letters 37 (1996), S. 163-165 
    Details
    ISSN: 1572-879X
    Keywords: nitrogen ; Rh(111) ; thermal desorption ; Arrhenius parameters ; lateral interactions ; NO decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Associative desorption of N atoms from the Rh(111) surface is simulated in the framework of the lattice-gas model. The Arrhenius parameters and nearest-neighbour lateral interaction employed to describe the measured thermal desorption spectra are as follows:v=1013 s−1,E d=40 kcal/mol, and ε1=1.7 kcal/mol. The results obtained are used to clarify the role of nitrogen desorption in the NO + CO reaction on Rh(111) atT=400–700 K andP NO≈P CO≈0.01 atm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807748
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  • 5
    Electronic Resource
    Electronic Resource
    FTIR spectroscopic evidence of formation of geminal dinitrogen species during the low-temperature N2 adsorption on NaY zeolites (1999)
    Springer
    Catalysis letters 58 (1999), S. 21-26 
    Details
    ISSN: 1572-879X
    Keywords: adsorption ; adsorption isotherms ; dinitrogen ; FTIR spectroscopy ; geminal species ; NaY ; nitrogen ; zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption of N2 on NaY zeolites at 85 K and equilibrium pressures higher than 1 kPa results in the formation of geminal dinitrogen complexes characterized by an IR band at 2333.5 cm−1 (2255.4 cm−1 after adsorption of 15N2). With decreasing equilibrium pressure the complexes tend to loose one N2 ligand, thus forming linear species characterized by an IR band at 2336.8 cm−1 (2258.7 cm−1 after adsorption of 15N2). All species disappear completely after evacuation. Co-adsorption of N2 and CO revealed that the dinitrogen complexes are formed on Na+ cations. The changes in the concentrations of the linear and geminal N2 species with the changes in the equilibrium pressure are excellently described by equations of adsorption isotherms proposed earlier for mono- and di-carbonyls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019040825491
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  • 6
    Electronic Resource
    Electronic Resource
    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of co-granulated nutrients and granule size on plant responses to elemental sulfur in compound fertilizers (1996)
    Springer
    Nutrient cycling in agroecosystems 46 (1996), S. 81-90 
    Details
    ISSN: 1573-0867
    Keywords: elemental sulfur ; granule size ; nitrogen ; phosphorus ; potassium ; S oxidation ; sulfur fertilizers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Experiments were undertaken to determine the effect of granule size and nutrients in granulated compound fertilizers fortified with finely divided elemental sulfur (So) on the rate of So oxidation. In one experiment, So was banded together with or apart from triple superphosphate (TSP) while in two others, So was granulated with nutrient and inert carriers. A fourth experiment examined response to S in an So-fortified TSP from a range of granule sizes. Response and, in some cases, So recovery (using 35S labels) by test crops (maize, wheat, upland rice) was measured. In all experiments, P mixed with So increased plant growth and S recovery above treatments in which P and So were physically separated. There was however, no effect of distance of separation on S recovery. In one experiment, N as urea and N and P as diammonium phosphate (DAP) were also found to enhance response to So although to a lesser degree than P alone. These observations were attributed to a nutritional requirement of So-oxidizing microorganisms for P and N. Granulation of So with carriers also influenced oxidation rate, as inferred from the fertilizer S recovery. For a given So concentration, the effect was inversely proportional to the mean diameter of granules. It is shown that this relationship can be explained if one assumes that So particles in granules collapse into a fixed number of aggregates per granule irrespective of granule size when the soluble nutrient carrier dissolves and diffuses away from the point of application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210226
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  • 8
    Electronic Resource
    Electronic Resource
    Direct emission of nitrous oxide from agricultural soils (1996)
    Springer
    Nutrient cycling in agroecosystems 46 (1996), S. 53-70 
    Details
    ISSN: 1573-0867
    Keywords: crop ; emission ; fertilizer ; nitrogen ; nitrous oxide ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This analysis is based on published measurements of nitrous oxide (N2O) emission from fertilized and unfertilized fields. Data was selected in order to evaluate the importance of factors that regulate N2O production, including soil conditions, type of crop, nitrogen (N) fertilizer type and soil and crop management. Reported N2O losses from anhydrous ammonia and organic N fertilizers or combinations of organic and synthetic N fertilizers are higher than those for other types of N fertilizer. However, the range of management and environmental conditions represented by the data set is inadequate for use in estimating emission factors for each fertilizer type. The data are appropriate for estimating the order of magnitude of emissions. The longer the period over which measurements are made, the higher the fertilizer-induced emission. Therefore, a simple equation to relate the total annual direct N2O−N emission (E) from fertilized fields to the N fertilizer applied (F), was based on the measurements covering periods of one year: E=1+1.25×F, with E and F in kg N ha-1 yr-1. This relationship is independent of the type of fertilizer. Although the above regression equation includes considerable uncertainty, it may be appropriate for global estimates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210224
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of temperature on nutrient release from slow-release fertilizers (1996)
    Springer
    Nutrient cycling in agroecosystems 46 (1996), S. 179-187 
    Details
    ISSN: 1573-0867
    Keywords: electrical conductivity ; leaching ; nitrogen ; pH ; phosphorus ; potassium ; release pattern ; slow-release fertilizers ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied the effect of temperature on the release of N, P, and K from slow-release fertilizers (SRF). The study was conducted in micro-lysimeters filled with moist peat medium. Increasing the temperature from 4 to 12°C slightly increased N release from three different slow-release N (SRN) carriers with different particle sizes and coating thicknesses. At 21°C the rate of release was significantly different than the other two temperatures. Urea formaldehyde (UF), sulphur coated urea (SCU) and coated calcium nitrate (CCN), incubated in sphagnum moss peat, released between 3 and 20% of the applied N in six weeks. For eight synthetic and organic NPK carriers, the release pattern was similar to UF and SCU. However, the leaching losses of N from the NPK fertilizers were up to twenty times more than for the SRN products. Except for Osmocote® and Duna, which released 30–40% of the applied N as mineral-N within six weeks, all other slow-release and slowly mineralized NPK carriers acted like readily water-soluble compound NPK. Temperature did not affect the nutrient release from NPK fertilizers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420552
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of split applications of cattle slurry and mineral fertilizer–N on the yield of silage maize in a slurry-based cropping system (1999)
    Springer
    Nutrient cycling in agroecosystems 53 (1999), S. 209-218 
    Details
    ISSN: 1573-0867
    Keywords: cattle slurry ; fertilizer splitting ; nitrogen ; recovery ; residual nitrogen ; Zea mays L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The recovery of soil mineral nitrogen (N) by crops, and its subsequent utilisation for dry matter (DM) production may be increased when the application of N is postponed until after crop emergence. The significance of this strategy for silage maize was studied in nine field experiments on Dutch sandy soils from 1983 to 1988. In five experiments the effect of slurry applied before planting at a rate of circa 66 m3 ha-1, was compared to the effect of a similar rate of which half was applied before planting and half at the 4–6 leaf stage. In the 4-6 leaf stage slurry was either injected or banded. In four other experiments the effect of mineral fertilizer-N splitting was studied. In these experiments, 30 m3 ha-1 cattle slurry, applied before planting, was supplemented with mineral fertilizer-N at rates ranging from 40 to 160 kg ha-1, either fully applied before crop emergence or split. When split, 40 kg ha-1 of the mineral fertilizer-N rate was banded at the 4–6 leaf stage. According to balance sheet calculations, substantial losses of slurry N and mineral fertilizer-N occurred during the growing season. Losses were compensated for, however, by apparent mineralization, ranging from 0.34 to 0.77 kg N ha-1 day-1. Split applications of cattle slurry had a significant positive effect on the DM yield in two out of five experiments compared to the conventional non-split application, but only when the post-emergence slurry application was banded which is no longer in accordance with present legislation. Split applications of mineral fertilizer-N had a significant positive effect in one experiment where rainfall was excessive but not in the others. The results provide insufficient evidence to recommend farmers to split applications. Soil mineral N sampling at the 4–6 leaf stage should hence be considered a control on the appropriateness of early N applications after exceptional weather conditions rather than a routine observation on which the post-emergence N dressing is to be based in a deliberate splitting strategy. Our data suggest that the financial return of a 40 kg ha-1 supplementation with mineral fertilizer-N, was questionable when more than 175 kg N ha-1 were found in the upper 0.6 m soil layer at the 4–6 leaf stage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009796021850
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  • 11
    Electronic Resource
    Electronic Resource
    Using nitrogen budgets to indicate nitrogen use efficiency and losses from whole farm systems: a comparison of three methodological approaches (1999)
    Springer
    Nutrient cycling in agroecosystems 53 (1999), S. 259-267 
    Details
    ISSN: 1573-0867
    Keywords: farming systems ; nitrogen ; nitrogen budgets ; sustainability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three approaches to nitrogen budgeting were developed and their ability to quantitatively describe nitrogen cycling in a fertilizer based and a grass–clover based beef system tested. Budgets ranged in complexity from the Economic Input:Output (EIO) budget, which accounted simply for purchases and sales of nitrogen over the farmgate, through the Biological Input:Output (BIO) budget, which included estimates of biological nitrogen fixation and attempted to partition losses into leaching and gaseous forms, to the Transfer:Recycle:Input:Output (TRIO) budget, which also accounted for key soil processes. Nitrogen unaccounted for in the fertilized system decreased with increasing budget complexity (285, 212 and 188 kg ha-1 yr-1 unaccounted for by the EIO, BIO and TRIO budgets, respectively). In the legume based grass–clover system, the EIO budget did not accurately describe total nitrogen inputs as it did not include 146 kg ha-1 yr-1 from symbiotic nitrogen fixation. In the grass–clover system, nitrogen unaccounted for was again greater using the BIO than the TRIO budget (103 and 79 kg ha-1 yr-1, respectively). In conclusion, the most complex budgeting approach (TRIO) was able to account for the fate of a greater proportion of nitrogen inputs than the simpler approaches. However, the perceived success of the different approaches was strongly dependent on the precise objective.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009793120577
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  • 12
    Electronic Resource
    Electronic Resource
    Nitrogen uptake and chlorophyll meter measurements in Spring Wheat (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 1-6 
    Details
    ISSN: 1573-0867
    Keywords: chlorophyll meter ; irrigation ; LAI ; nitrogen ; Spring Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A Spring Wheat crop was grown using three irrigation levels and nitrogen rate applications to evaluate chlorophyll meter measurements as a possible nitrogen nutrition index for modelling. These measurements yielded the most reliable indications at Zadoks GS45. The lower limit indicating severe nitrogen deficiency in the leaves was approximately 35 SPAD units while the upper limit of 45 SPAD units, indicated an excess consumption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009843813004
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  • 13
    Electronic Resource
    Electronic Resource
    The fate of algal nitrogen in a flooded soil system (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 89-94 
    Details
    ISSN: 1573-0867
    Keywords: algae ; flooded soils ; N cycling ; nitrogen ; 15N ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Algal N labelled with 15N added to a flooded soil in laboratory columns without plants was studied to determine the changes over time in the fate of N assimilated by algae and to study how its fate is affected by (a) exclusion of light simulating complete closure of the rice canopy, and (b) addition of fertilizer-NH4 *. In the light but with no added fertilizer-N there was little net mineralization of the added algal N during the first 4 weeks, but after 8 weeks 42% had been mineralized, of which 95% was denitrified. Exclusion of light caused net mineralization to proceed more rapidly in the first 4 weeks due to the death of algal cells and lowered reassimilation. After 8 weeks 51% had been mineralized, of which 54% was denitrified, 16% volatilized and 30% was present as KCl exchangeable NH4 +-N. Application of fertilizer-NH4 + apparently caused mineralization of 25% of the algal N within one week but the results were probably affected by pool substitution in which labelled N mineralized to NH4 +-N was diluted with fertilizer – NH+ 4 and then immobilized leaving more labelled NH4–N in the mineral pool. After 8 weeks, 42% of algal N had been mineralized, of which 69% was estimated to have been denitrified, 19% lost through NH3 volatilization and 12% remained as extracted NH4 ++NO- 3. Uptake of N by a rice crop would reduce the gaseous losses. Algal N was mineralized quickly enough to be available during the growing season of a rice crop and, depending on field conditions, algae may have a role in assimilating N and protecting it from loss as well as being a major driving force for NH3 volatilization through diurnal increases in pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009850915579
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  • 14
    Electronic Resource
    Electronic Resource
    The value of poultry manure for wetland rice grown in rotation with wheat (1996)
    Springer
    Nutrient cycling in agroecosystems 47 (1996), S. 243-250 
    Details
    ISSN: 1573-0867
    Keywords: fertilizer value ; nitrogen ; phosphorus ; poultry manure ; urea ; wetland rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Poultry manure applied alone or in combination with urea at different N levels was evaluated as a N source for wetland rice grown in a Fatehpur loamy sand soil. Residual effects were studied on wheat which followed rice every year during the three cropping cycles. In the first year, poultry manure did not perform better than urea but by the third year, when applied in quantities sufficient to supply 120 and 180 kg N ha−1, it produced significantly more rice grain yield than the same rates of N as urea. Poultry manure sustained the grain yield of rice during the three years while the yield decreased with urea. Apparent N recovery by rice decreased from 45 to 28% during 1987 to 1989 in the case of urea, but it remained almost the same (35, 33 and 37%) for poultry manure. Thus, urea N values of poultry manure calculated from yield or N uptake data following two different approaches averaged 80, 112 and 127% in 1987, 1988 and 1989, respectively. Poultry manure and urea applied in 1:1 ratio on N basis produced yields in between the yields from the two sources applied alone. After three cycles of rice-wheat rotation, the organic matter in the soil increased with the amount of manure applied to a plot. Olsen available P increased in soils amended with poultry manure. A residual effect of poultry manure applied to rice to supply 120 or 180 kg N ha−1 was observed in the wheat which followed rice and it was equivalent to 40 kg N ha−1 plus some P applied directly to wheat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01986279
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  • 15
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    Electronic Resource
    Influence of Canopy Height and Fertilization Levels on the Resistance of Lycopersicon Hirsutum to Aculops Lycopersici (Acari: Eriophyidae) (1999)
    Springer
    Experimental and applied acarology 23 (1999), S. 633-642 
    Details
    ISSN: 1572-9702
    Keywords: tomato plants ; susceptibility ; mite ; tridecan-2-one ; nitrogen ; potasium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objective of this work was to study the effect of NK fertilization levels and canopy height on the resistance of Lycopersicon hirsutum and Lycopersicon esculentum to Aculops lycopersici (Acari: Eriophydae). The effects of NK fertilization levels and canopy height in the leaf size and density of trichomes and their effects on tridecan-2-one (2-TD) and undecan-2-one (2-UD) limiting the attack of A. lycopersici on tomato plants were assessed. Different NK fertilization levels had no effect on the resistance of L. hirsutum to A. lycopersici. No significant differences were found in attack rates of this mite on leaves of the top and median parts of L. hirsutum canopy. The type and density of trichomes were the main determining factor of A. lycopersici attack on tomato plants. High trichome densities and type VI glandular trichomes which produce tridecan-2-one are important resistance factors on tomato plants. L. hirsutum showed a high resistance level to A. lycopersici due to high densities of type VI glandular trichomes and consequently higher levels of tridecan-2-one in its leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006201915292
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  • 16
    Electronic Resource
    Electronic Resource
    Effect of landscape position on the sediment chemistry of abandoned-channel wetlands (1996)
    Springer
    Landscape ecology 11 (1996), S. 27-38 
    Details
    ISSN: 1572-9761
    Keywords: abandoned channels ; floodplain ; nitrogen ; organic matter ; phosphorous ; potassium ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nature of sediments in abandoned channels is an important component of their development as floodplain wetlands. The texture, organic matter, phosphorous, potassium, and nitrogen content of sediments were determined for abandoned channels along the Iowa and Cedar Rivers near their confluence in Iowa. Differences in the levels of these constituents were examined among categories of three landscape gradients: present connectivity to the river, time since abandonment, and proximity to agricultural land use. Local scale processes of ecological development are seen in the importance of time for increased organic matter and nitrogen. Basin scale processes of sediment transport and deposition are revealed by the importance of connectivity for decreases in these two elements, and by the counter-intuitive findings for nitrogen and especially phosphorous and potassium in relation to agricultural proximity. Location on a floodplain is important for differentiating development, but it cannot be reduced to univariate gradients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02087111
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  • 17
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    A GIS-based index for relating landscape characteristics to potential nitrogen leaching to wetlands (1996)
    Springer
    Landscape ecology 11 (1996), S. 237-255 
    Details
    ISSN: 1572-9761
    Keywords: wetlands ; non-point source pollution ; nitrogen ; watershed ; leaching ; geographic information system ; landscape ; groundwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We developed a spatially-explicit, quantitative Nitrogen Leaching Index to assess the potential for non-point source subsurface nitrogen pollution to wetlands. The index was based on the leaching potential of the watershed soils, the amount of nitrogen available for leaching, and the spatial position of nitrogen sources in the watershed. A raster or cell-based geographic information system (GIS) was used to estimate the necessary data inputs for calculating the index, such as soil hydrologic group, land use/soil type combination, groundwater residence time, and location of septic systems. The Total and Average Watershed Nitrogen Leaching Index (TWNLI and AWNLI) were calculated by summing and averaging, respectively, individual cell contributions over a watershed. Analysis of nine wetland watersheds in central New York state, USA, with mixed forest and agricultural land uses illustrated the use of the index for identifying and ranking wetlands with potential nitrogen pollution. Results showed that the spatial characteristics of a watershed potentially can effect subsurface nitrogen delivery to groundwater-dominated wetlands. The use of an index based on watershed soils, topography, and land use may be useful for assessing potential nitrogen pollution to wetlands at a regional scale.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02071814
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    The behavior of titanium, stainless steel, and copper-nickel alloys as plasma torch cathodes (1996)
    Springer
    Plasma chemistry and plasma processing 16 (1996), S. 577-603 
    Details
    ISSN: 1572-8986
    Keywords: Cathode erosion ; electrode materials ; argon ; nitrogen ; hydrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Cathode erosion continues to be a problem hindering the widespread application of plasma technology. In this work, cathode erosion was studied on titanium, stainless steel 314, copper-nickel 10% and 30%, and copper 122 for magnetically rotated arcs operating in argon, nitrogen, and argon/hydrogen mixtures at a constant magnetic flux density of 0.1 T Titanium and stainless steel gave very low erosion rates in argon (0.2 and 0.3, μg/C respectively). Cupronickels were shown to be suitable for nitrogen and hydrogen plasmas. The slope of hydrogen solubility versus temperature in the cathode material was found to be important in determining hydrogen plasma erosion characteristics. When the plasma gas has a high solubility in the cathode material, or can react with the cathode, a negative erosion rate may result. When gas solubility in the cathode is low, oxide stability and mode of electron emission may govern the erosion rate. A high gas solubility in the cathode material, as with hydrogen, can result in mechanical erosion due to micro-explosions near the cathode surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01447010
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  • 19
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    Nitrogen Addition to an O-1 Tool Steel (1999)
    Springer
    Journal of materials synthesis and processing 7 (1999), S. 311-319 
    Details
    ISSN: 1573-4870
    Keywords: Iron ; carbon ; nitrogen ; microstructure ; characterization ; HIP-drip
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new processing technique makes nitrogen alloying possible by adding nitrogen under elevated nitrogen pressure to prealloyed Fe-C ingots during continuous casting, producing a whole new class of precipitation-free, iron–carbon–nitrogen alloys. When both carbon and nitrogen bulk concentration levels exceeded 0.5 wt%, a duplex fcc-/(bcc-bct-) Fe microstructure resulted that is iron carbide- and nitride-free. With increasing carbon and nitrogen concentrations, there was an increase in the retained fcc-Fe phase. In cooling rate studies, increasing carbon and nitrogen concentrations shifted the knee of the fcc-Fe-to-bcc-Fe phase time–temperature–transformation (T–T–T) curve to longer times. Hardness, compression strength, and wear resistance increased with increasing carbon and nitrogen concentrations and were superior to iron–carbon alloys without the nitrogen addition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021877121902
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  • 20
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    Biogeochemistry of a forested watershed in the central Adirondack Mountains: Temporal changes and mass balances (1996)
    Springer
    Water, air & soil pollution 88 (1996), S. 355-369 
    Details
    ISSN: 1573-2932
    Keywords: atmospheric deposition ; ecosystem ; hydrology ; nitrogen ; sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Information on atmospheric inputs, water chemistry and hydrology were combined to evaluate elemental mass balances and assess temporal changes in elemental transport from 1983 through 1992 for the Arbutus Lake watershed. This watershed is located within a northern hardwood ecosystem at the Huntington Forest within the central Adirondack Mountains of New York (USA). Changes in water chemistry, including increasing NO3 − concentrations (1.1 μmol c , L−1 yr-1), have been detected during this study period. Starting in 1991 hydrological flow has been measured from Arbutus Lake and these measurements were compared with predicted flow using the BROOK2 hydrological simulation model. The model adequately (r2=0.79) simulated flow from this catchment and was used to estimate drainage for earlier periods when direct hydrological measurements were not available. Modeled drainage water losses coupled with estimates of wet and dry atmospheric deposition were used to calculate solute budgets. Export of SO4 2− (831 mol c ha−1 yr−1) from the greater Arbutus Lake watershed exceeded estimates of atmospheric deposition in an adjacent hardwood stand suggesting an additional source of S. These large drainage losses of SO4 2− also contributed to the drainage fluxes of basic cations (Ca2+, Mg2+, K+ and Na+). Most of the atmospheric inputs of inorganic N were retained (average of 74% of wet precipitation and 85% total deposition) in the watershed. There were differences among years (56 to 228 mol ha−1 yr−1) in drainage water losses of N with greatest losses occurring during a warm, wet period (1989–1991).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294111
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  • 21
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    Chemical characteristics of leachate from pulp and paper mill residuals used to reclaim a sandy soil (1996)
    Springer
    Water, air & soil pollution 89 (1996), S. 167-187 
    Details
    ISSN: 1573-2932
    Keywords: Pulp and paper mill sludge ; nitrogen ; DOC ; heavy metals ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Primary sludge, secondary sludge, and wood ash from a pulp and paper mill were combined with sand to create a synthetic topsoil (C:N ratio of 18:1) to restore an abandoned gravel pit. Synthetic topsoil was applied to field microcosms at rates equivalent to 0, 2170, 4341, or 6511 kg N/ha; each was seeded with grass. Fifteen chemical constituents in leachate were measured during two field seasons. Cadmium, Ni and Zn were mobilized rapidly by soil disturbance. Chloride and SO4-S eluted rapidly from the sludge along with Na. Nitrate leached with Ca late in each field season when sludge N-mineralization and nitrification exceeded plant uptake and microbial immobilization. Ammonium elution was negligible. Dissolved organic carbon (DOC) was mobilized by decomposition of organic matter in the sludge, as were Mg and K. Copper eluted with DOC, probably as an organic ligand. Lead and ortho-P were below our detection limits. We concluded that a synthetic topsoil with a 30:1 C:N ratio applied at a rate of 2100-4300 kg N/ha should provide adequate plant nutrition while minimizing water quality hazards.
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    URL: http://dx.doi.org/10.1007/BF00300429
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  • 22
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    Characterization ofVitis vinifera L. glutamine synthetase and molecular cloning of cDNAs for the cytosolic enzyme (1996)
    Springer
    Plant molecular biology 31 (1996), S. 983-992 
    Details
    ISSN: 1573-5028
    Keywords: cDNA cloning ; gene expression ; glutamine synthetase ; grapevine ; nitrogen ; Vitis vinifera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Grapevine (Vitis vinifera L.) glutamine synthetase (GS) was analysed into two distinct classes of isoforms; one of them was present in both leaf and root tissues while the other one showed leaf specificity. Western blot analysis revealed that grapevine GS consists of three types of polypeptides of distinct size and differential tissue specificity. Two structurally distinct cDNA clones, pGS1;1 and pGS1;2, encoding grapevine GS were isolated from a cell suspension library and characterized. Both clones contained open reading frames encoding for polypeptides of 356 amino acids with a predicted molecular mass of about 39 kDa. Although the coding sequences of pGS1;1 and pGS1;2 were 84% similar, their 5′-and 3′-untranslated sequences showed only 40% similarity. The coding sequences of the two clones and the derived amino acid sequences showed higher homology to cytosolic than to chloroplastic GSs of other higher plants indicating that the cDNAs isolated encode for cytosolic isoforms of grapevine GS. Southern blot analysis suggested the existence of more than two GS genes in the grapevine genome. In northern blots both clones were hybridized to mRNAs of about 1.4 kb that are differentially expressed in the various tissues. Supply of nitrate or ammonium in the cell suspension culture medium, as a sole nitrogen source, resulted in differential response of the pGS1;1-and pGS1;2-related genes.
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    URL: http://dx.doi.org/10.1007/BF00040717
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  • 23
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    Improving the field performance of micro-and minitubers (1999)
    Springer
    Potato research 42 (1999), S. 559-568 
    Details
    ISSN: 1871-4528
    Keywords: plastic mulch ; transplanting ; nitrogen ; planting depth ; seed tuber weight ; physiological age ; radiation conversion efficiency ; harvest index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In many seed potato producing areas, micro- and minitubers are too small for direct planting as seed tubers in the field. Such use of these propagules can, however, be feasible if the crop's growth and development can be advanced. Increasing light interception, harvest index and yield of useable progeny tubers has been proved possible with plastic mulch and pre-planting of small tubers in a greenhouse. High amounts of nitrogen (up to 180 kg ha−1) or deep planting (up to 9 cm) were less effective. Using older or pre-sprouted micro- or minitubers may be beneficial, because this might increase the number of sprouts per mother tuber (and thus stems per plant) or advance the growth of sprouts or stems. However, this would require even more careful management, due to the weakness of these sprouts and stems. Micro- and minitubers should be as large as feasible when used for direct planting in the field.
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    URL: http://dx.doi.org/10.1007/BF02358172
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    Adsorption of a four-component gas mixture on zeolite NaX (1996)
    Springer
    Russian chemical bulletin 45 (1996), S. 794-796 
    Details
    ISSN: 1573-9171
    Keywords: nitrogen ; methane ; ethane ; propane ; combined adsorption ; zeolite NaX ; selectivity coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption of N2, CH4, C2H6, C3H8, and their mixture on zeolite NaX was studied by the volumetric method under static conditions at 278 K in the pressure range from 0.1 to 0.8 MPa. Compressibility factors were calculated in order to take into account the nonideal character of the gas phase. Adsorption isotherms of individual gases and partial isotherms were obtained. The adsorption properties of gases in the adsorption of a mixture and its components were compared. The selectivity coefficient of adsorption of propane in the N2-CH4-C2H6-C3H8-NaX system was calculated, and its dependence on the total pressure was determined.
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    URL: http://dx.doi.org/10.1007/BF01431299
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    The nutrient translocation of seedlings with chemical analyses of the xylem saps ofCryptomeria japonica D. Don andPinus densiflora Sieb. et Zucc. (1996)
    Springer
    Journal of forest research 1 (1996), S. 23-25 
    Details
    ISSN: 1610-7403
    Keywords: calcium ; mineral distribution ; nitrogen ; potassium ; xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The chemical compositions of xylem saps ofCryptomeria japonica D. Don andPinus densiflora Sieb. et Zucc. were studied. One-year-old seedlings of these species were transplanted into hydroponics in the middle of June. Some seedlings were retained in the nursery. Two nitrogen sources, ammonium and nitrate nitrogen, were applied separately. The samplings of xylem saps were made at the end of July. Saps were collected from both roots and tops of the seedlings using a pressure chamber. InC. japonica, the fact that the translocation form of nitrogen from the roots to shoots mainly was citrulline was confirmed. The result ofP. densiflora in this study showed that glutamine was the predominant compound of nitrogen translocation. Total nitrogen ofP. densiflora had a large value in the series of ammonium. Glutamine increased in the ammonium series of both species. Nitrate nitrogen was found in whole samples ofC. japonica, and was not found inP. densiflora. As the result of cations in the saps, monovalent cations were rich inP. densiflora, and divalent cation concentrations were greater inC. japonica. The idea that the great oxygen requirement ofP. densiflora produces the negative charge gives an explanation of the great retention of divalent cations in the roots. The idea that the mineral distribution indicates root activity related to its negative charge production also is considered a possibility.
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    URL: http://dx.doi.org/10.1007/BF02348335
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    Retention of nutrients in river basins (1999)
    Springer
    Aquatic ecology 33 (1999), S. 29-40 
    Details
    ISSN: 1573-5125
    Keywords: denitrification ; nature restoration ; nitrogen ; phosphorus ; riparian areas ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Denmark, as in many other European countries, the diffuse losses of nitrogen (N) and phosphorus (P) from the rural landscape are the major causes of surface water eutrophication and groundwater pollution. The export of total N and total P from the Gjern river basin amounted to 18.2 kg ha−1 and 0.63 kg P ha−1 during June 1994 to May 1995. Diffuse losses of N and P from agricultural areas were the main nutrient source in the river basin contributing 76% and 51%, respectively, of the total export. Investigations of nutrient cycling in the Gjern river basin have revealed the importance of permanent nutrient sinks (denitrification and overbank sedimentation) and temporary nutrient storage in watercourses. Temporary retention of N and P in the watercourses thus amounted to 7.2–16.1 g N m−2 yr−1 and 3.7–8.3 g P m−2 yr−1 during low-flow periods. Deposition of P on temporarily flooded riparian areas amounted from 0.16 to 6.50 g P m−2 during single irrigation and overbank flood events, whereas denitrification of nitrate amounted on average to 7.96 kg N yr−1 per running metre watercourse in a minerotrophic fen and 1.53 kg N yr−1 per linear metre watercourse in a wet meadow. On average, annual retention of N and P in 18 Danish shallow lakes amounted to 32.5 g N m−2 yr−1 and 0.30 g P m−2 yr−1, respectively, during the period 1989–1995. The results indicate that permanent nutrient sinks and temporary nutrient storage in river systems represent an important component of river basin nutrient budgets. Model estimates of the natural retention potential of the Gjern river basin revealed an increase from 38.8 to 81.4 tonnes yr−1 and that P-retention increased from −0.80 to 0.90 tonnes yr−1 following restoration of the water courses, riparian areas and a shallow lake. Catchment management measures such as nature restoration at the river basin scale can thus help to combat diffuse nutrient pollution.
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    URL: http://dx.doi.org/10.1023/A:1009947907811
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  • 27
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    Recent changes in the contributions of river Rhine and North Sea to the eutrophication of the western Dutch Wadden Sea (1996)
    Springer
    Aquatic ecology 30 (1996), S. 27-39 
    Details
    ISSN: 1573-5125
    Keywords: Eutrophication ; nutrients ; phosphorus ; nitrogen ; chlorophyll-a ; primary production ; secondary production ; Mytilus edulis ; river Rhine ; Wadden Sea ; North Sea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From 1955 to the mid 1980s the loads of both nitrogen and phosphorus from the river Rhine to the Dutch coastal area, the Wadden Sea included, increased. Since 1985 the phosphorus loads has decreased significantly, while the nitrogen load remained about the same. Annual primary production in the western Dutch Wadden Sea has increased fromc. 40 g C m−2 (1950) to 150 (mid 1960s) and over 500 g C m−2 (1986). The biomass of macrozoobenthos has more than doubled since 1970. Simultaneously, the meat yield of cultured blue mussels (Mytilus edulis), has increased since the 1960s. Previously, it was indicated that the increase in primary production of the phytoplankton over the period 1950 to 1986 was stimulated by the load of dissolved inorganic phosphate from Lake IJssel, a reservoir supplied by Rhine water. Since 1990, however, primary production has been higher than was expected from decreased phosphate loads from Lake IJssel. It is argued that this lack of response may have been caused by increased concentrations of dissolved inorganic phosphate at sea originating from increased inflow from a.o. the Strait of Dover, which compensate for the decrease in phosphate from the rivers, possibly in combination with a significant improvement of the light conditions of the water in the Wadden Sea.
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    URL: http://dx.doi.org/10.1007/BF02092145
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    Variation in nutrient availability and plant species diversity across forb and graminoid zones of a Northern New England high salt marsh (1999)
    Springer
    Plant ecology 143 (1999), S. 219-228 
    Details
    ISSN: 1573-5052
    Keywords: mineralization ; nitrogen ; phosphorus ; salinity ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant zonation patterns across New England salt marshes have been investigated for years, but how nutrient availability differs between zones has received little attention. We investigated how N availability, P availability, and plant N status varied across Juncus gerardii, Spartina patens, and mixed forb zones of a Northern New England high salt marsh. We also investigated relationships between several edaphic factors and community production and diversity across the high marsh. P availability, soil salinity, and soil moisture were higher in the mixed forb zone than in the two graminoid zones. NH+ 4-N availability was highest in the J. gerardii zone, but NO− 3-N availability and mid season net N mineralization rates did not vary among zones. Plant tissue N concentrations were highest in the mixed forb zone and lowest in the S. patens zone, reflecting plant physiologies more so than soil N availability. Community production was highest in the J. gerardii zone and was positively correlated with N availability and negatively correlated with soil moisture. Plant species diversity was highest in the mixed forb zone and was positively correlated with P availability and soil salinity. Thus, nutrient availability, plant N status, and plant species diversity varied across zones of this high marsh. Further investigation is needed to ascertain if soil nutrient availability influences or is a result of the production and diversity differences that exist between vegetation zones of New England high salt marshes.
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    URL: http://dx.doi.org/10.1023/A:1009887727465
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    Denitrification in coastal ecosystems: methods, environmental controls, and ecosystem level controls, a review (1999)
    Springer
    Aquatic ecology 33 (1999), S. 41-54 
    Details
    ISSN: 1573-5125
    Keywords: denitrification ; eutrophication ; estuary ; nitrogen ; sediment-water exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this review of sediment denitrification in estuaries and coastal ecosystems, we examine current denitrification measurement methodologies and the dominant biogeochemical controls on denitrification rates in coastal sediments. Integrated estimates of denitrification in coastal ecosystems are confounded by methodological difficulties, a lack of systematic understanding of the effects of changing environmental conditions, and inadequate attention to spatial and temporal variability to provide both seasonal and annual rates. Recent improvements in measurement techniques involving 15 N techniques and direct N2 concentration changes appear to provide realistic rates of sediment denitrification. Controlling factors in coastal systems include concentrations of water column NO 3 − , overall rates of sediment carbon metabolism, overlying water oxygen concentrations, the depth of oxygen penetration, and the presence/absence of aquatic vegetation and macrofauna. In systems experiencing environmental change, either degradation or improvement, the importance of denitrification can change. With the eutrophication of the Chesapeake Bay, the overall rates of denitrification relative to N loading terms have decreased, with factors such as loss of benthic habitat via anoxia and loss of submerged aquatic vegetation driving such effects.
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    URL: http://dx.doi.org/10.1023/A:1009921414151
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    Environmental effects on growth and biochemical composition ofNitzschia inconspicua Grunow (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 389-396 
    Details
    ISSN: 1573-5176
    Keywords: Nitzschia inconspicua ; diatoms ; lipids ; fatty acids ; eicosapentaenoic acid ; silicate ; nitrogen ; carbon source
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nitrate and silicate levels, and carbon source on growth, biochemical composition and fatty acid composition ofNitzschia inconspicua were investigated using batch cultures. Within the range of silicate levels supplied (8.8–176 μM), no marked variations in growth trend, biochemical composition or fatty acid composition were shown. Biomass at stationary phase, ranging from 64–66 mg ash-free dry weight (AFDW) L−1, and specific growth rate (μ) based on chlorophylla (0.41–0.50 d−1) of the cultures grown within 0.3–3.0 mM NaNO3 were not significantly different. Cultures supplemented with glucose (0.1 % w/v), acetate (0.1 % w/v) or 5% CO2 attained higher biomass (85, 85, 97 mg AFDW L−1) than the control which was grown in synthetic seawater and agitated by magnetic stirring. Cells grown at 〈3.0 mM NaNO3 contained higher carbohydrate contents (14.8–21.5% AFDW) than those grown at 3.0 mM (4.0% AFDW). Lipid content increased at the expense of proteins in cells aerated with 5% CO2. The dominant fatty acids, 16:0 and 16:1, ranged from 35.7–45.0% and 36.4–45.4% total fatty acids (TFA), respectively, while the relative proportions of 20:4 (n-6) and 20:5 (n-3) ranged from 1.7–5.4% and 3.4–5.9% TFA respectively. Cultures aerated with 5% CO2 attained the highest biomass (97 mg AFDW L−1) and yield of 20:5 (n-3) (0.34 mg L−1).
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    URL: http://dx.doi.org/10.1007/BF02178582
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    Effect of meteorology and nutrient load on oxygen depletion in a Danish micro-tidal estuary (1999)
    Springer
    Aquatic ecology 33 (1999), S. 55-64 
    Details
    ISSN: 1573-5125
    Keywords: estuaries ; nitrogen ; oxygen depletion ; phosphorus ; regression model ; vertical mixing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a detailed analysis of oxygen saturation in a shallow Danish estuary it was possible to separate the effect of meteorological forcings (i.e. wind and solar radiation) and nutrient loads on oxygen depletion in bottom water. Regression analysis showed that oxygen saturation tied to nitrogen load rather than to phosphorus load. During summer periods of stratification the oxygen saturation could be attributed to the time elapsed after the onset of stratification and the accumulated nitrogen loading 10 month prior to measurement. Using a 10-year meteorological database and an empirical model it was calculated that a 25% reduction in nitrogen loading would reduce the number of days with severe oxygen depletion (i.e. 〈15% of saturation) by more than 50%.
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    URL: http://dx.doi.org/10.1023/A:1009956210537
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    Effects of Potato-cyst Nematodes (Globodera pallida) and Soil pH on Root Growth, Nutrient Uptake and Crop Growth of Potato (1999)
    Springer
    European journal of plant pathology 105 (1999), S. 61-76 
    Details
    ISSN: 1573-8469
    Keywords: core sampling ; foliar nutrient concentrations ; minirhizotrons ; nitrogen ; phosphorus ; potassium ; Rhizolab
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Potato-cyst nematodes (Globodera pallida) cause severe yield losses in potato. Plants infected with potato-cyst nematodes generally have reduced concentrations of nitrogen, phosphorus and potassium in the foliage. This study investigated whether reduced growth of nematode-infected potato is caused by nutrient limitation. Experiments in the field and in containers showed that phosphorus concentration correlated best with total crop biomass at early stages of growth. The role of phosphorus in nematode damage was further investigated in the field and in the Wageningen Rhizolab. The experimental field was infested with potato-cyst nematodes and two levels of nematode density were established by fumigation with a nematicide. Prior applications of calcium carbonate resulted in pHKCl levels of 4.8 and 6.1. Two levels of phosphorus fertiliser were applied: either 0 or 225 kg P ha−1. In the Wageningen Rhizolab, soil of both pH levels from the field was used after treatment with 1 MRad gamma irradiation to kill the nematodes. Subsequently, half of the soil was inoculated with cysts to give a nematode density of 30 viable juveniles per gram of soil. In the field, nine weeks after planting, the total crop biomass ranged from 107 g m−2 for the treatment with nematodes at pHKCl 6.1 without phosphorus fertiliser to 289 g m−2 for the fumigated treatment at pHKCl 4.8 with phosphorus fertiliser. The differences in total biomass for the various treatments were explained by differences in foliar phosphorus concentration. Nematodes induced or aggravated P deficiency and reduced total biomass. This was not the only damage mechanism as at high, non-limiting levels of foliar phosphorus concentration, nematodes still reduced total biomass. In the Wageningen Rhizolab, directly after planting, the number of roots visible against minirhizotrons was reduced by nematodes. However, the increase of root number in the nematode treatment continued longer than in the control, until root number was higher than that of the control. The compensary root growth of the nematode treatment was restricted to the top 30 cm and nematodes reduced rooting depth. High soil pH reduced growth, mainly by reducing the availability of phosphate. Both nematodes and high soil pH reduced nutrient uptake per unit root length. Our results lead us to suggest an interaction between nematodes and soil pH, with nematode damage being higher at pHKCl 6.1 than at pHKCl 4.8.
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    URL: http://dx.doi.org/10.1023/A:1008641511688
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    Deposition Rates of Terrestrial and Marine Organic Carbon in the Osaka Bay, Seto Inland Sea, Japan, Determined Using Carbon and Nitrogen Stable Isotope Ratios in the Sediment (1999)
    Springer
    Journal of oceanography 55 (1999), S. 1-11 
    Details
    ISSN: 1573-868X
    Keywords: Osaka Bay ; sediment ; carbon ; nitrogen ; organic matter ; stable isotope ratio ; terrestrial organic matter ; TOC ; POC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Carbon and nitrogen stable isotope ratios (δ13C and δ15N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The δ13C and δ15N of surface sediments in the estuary of the Yodo River were less than −23‰ and 5‰ respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving δ13C of about −20‰ and δ15N about 6‰). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.
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    Wastewater Irrigation-Economic Concerns Regarding Beneficiary and Hazardous Effects of Nutrients (1999)
    Springer
    Water resources management 13 (1999), S. 303-314 
    Details
    ISSN: 1573-1650
    Keywords: economics ; irrigation ; nitrogen ; nutrients ; wastewater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The optimal wastewater treatment level is affected by costs, hazards and benefits. Lowering the wastewater treatment level decreases fertilization costs because of the increased levels of available nutrients left in the water, and irrigation costs decrease if water prices reflect the lower treatment costs. Agricultural yields and/or prices may decrease according to differences between levels of nutrients needed by crops and those available in wastewater. The present article focuses on determination of monthly optimal treatment levels and of the mix of crops calculated to maximize agricultural incomes, according to farmers' point of view. It does not reflect the national point-view focusing on maximization of net national benefits considering also environmental hazards. The methodology appears in Haruvy (1994) and application will be presented in another article (Haruvy et al., 1999).
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    Comparison of solutes, nutrients, and bacteria inputs from two types of groundwater to the Rhône river during an artificial drought (1996)
    Springer
    Hydrobiologia 319 (1996), S. 65-72 
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    ISSN: 1573-5117
    Keywords: river ; hyporheic ; dissolved organic carbon ; nitrogen ; phosphorus ; silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Solute, nutrient and bacterial inputs to the River Rhône from the interstitial habitat of a gravel bar and the floodplain aquifer were investigated during an artificial drought. Eight springs were investigated: four groundwater-fed springs in the floodplain, located at the bottom of the bank; and four interstitial-fed springs located at the downstream end of a gravel bar. During this period, the inflows of groundwater to the river represented an average input of 0.77 mg l−1 of nitrogen (of which 93.3% were nitrates), 0.0187 mg l−1 of total phosphorus (of which 42.2% was orthophosphate), 3.56 mg l−1 of silica, 2.315 ± 0.703 mg l−1 of dissolved organic carbon (DOC, of which 47% was biodegradable) and 7.3 × 104 ± 3.7 × 104 bacteria per ml (of which 8.8% were active). Silica, DOC, biodegradable DOC, and bacteria concentrations displayed temporal variations during the study, which seem to be linked to the biological activity of the groundwater biofilm. There was a strong heterogeneity between the two types of groundwater that flow to the river: concentrations of calcium and alkalinity were higher in bank springs than in gravel bars springs. In these latters, sulfate, sodium, nitrogen, phosphorus were significantly higher.
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    Benthic oxygen respiration, ammonium and phosphorus regeneration in surficial sediments of the Sacca di Goro (Northern Italy) and two French coastal lagoons: a comparative study (1996)
    Springer
    Hydrobiologia 329 (1996), S. 143-159 
    Details
    ISSN: 1573-5117
    Keywords: Sediment ; nitrogen ; phosphorus ; regeneration ; iron availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During 1994 net sediment-water fluxes of oxygen, ammonium and inorganic phosphorus as well as sediment profiles of organic matter, nitrogen, phosphorus and iron were determined in three shallow eutrophic environments. Investigations were conducted monthly from March to December at five stations in the Sacca di Goro (Po River Delta, Italy). In the late summer, samples were collected from a single site in the Prévost lagoon (French Mediterranean coast) and three stations in the Bassin d'Arcachon (French Atlantic coast). In the Sacca di Goro, water-sediment exchanges of O2, NH 4 + and PO 4 3− were estimated by means of core incubation in the dark. Benthic fluxes for the French lagoons were in part determined experimentally using benthic chambers and in part from the literature. In general in the Sacca di Goro the highest oxygen uptake and nutrient release rates were found at the central sites, affected by macroalgal growth. At the sampling site adjacent to the freshwater inlet, sediment-water exchanges were principally influenced by tidal activity. In terms of organic matter and nutrient levels, sediments from the Sacca di Goro and from the Prévost lagoon, both colonised by the floating macroalga Ulva rigida C. Agardh, were similar. Sediments from the inner sheltered site in the Bassin d'Arcachon, invaded by the rooted macrophyte Ruppia cirrhosa (Pet.) Grande, showed the highest total N and P content (363 ± 157 µmol N cm−3 and 15 ± 2 µmol P cm−3 as average values in the top 10 cm of sediment), but were low in pore water ammonium and orthophosphate probably due to the high sequestering capacity of the system and/or efficient coupling between bacterial nutrient regeneration and assimilation by the plant roots. In addition the outer tidal stations in the Bassin d'Arcachon, invaded by rooted macrophytes, were low in pore water nutrients. A different trend was evident in the Prévost lagoon where the concentrations of exchangeable inorganic phosphorus and ammonium were appreciable (0.28 ± 0.07 µmol P cm−3 and 2.4 ± 1.4 µmol N cm−3 as average values in the top 10 cm of sediment). High amounts of dissolved organic nitrogen were found in the pore water at all the sites investigated showing the key role of the organic nitrogen in the recycling of nitrogen in these systems. The hypothesis that iron is a key factor in controlling phosphorus release is discussed since the Sacca di Goro, which is subject to dystrophic crises, is richer in iron than the Bassin d'Arcachon, which is a more buffered system.
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    Carbon and nitrogen stable isotope ratios of deposit-feeding polychaetes in the Nanakita River Estuary, Japan (1996)
    Springer
    Hydrobiologia 321 (1996), S. 69-75 
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    ISSN: 1573-5117
    Keywords: Nanakita River Estuary ; isotope ratio ; carbon ; nitrogen ; deposit-feeding polychaetes ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two types of deposit-feeding polychaetes, Neanthes japonica and Notomastus sp., and their surrounding sediments were collected from the Nanakita River Estuary and a small brackish lagoon (Gamõ Lagoon) in northeastern Japan. The samples were examined using stable isotope analysis to assess the site specific feeding mode of the animals and their trophic status. N. japonica is a surface deposit-feeder and Notomastus sp. is a subsurface deposit-feeder. In the estuary, the sedimentary δ 5N tended to become isotopically heavier from the upper estuary (2.0 ∼ 3.9‰) to the river mouth (4.3 ∼ 6.2‰), while sedimentary organic δ 13C constant value (−26.8 ∼ −24.4, average −25.6‰) throughout the river estuary. The δ 13C values of N. japonica were similar to those of the surrounding sediment in the upper estuary, whereas in the lower estuary, N. japonica had a heavier δ 13C value than the surrounding sediment. The δ 13C and dg 15N values indicated that the carbon, but not the nitrogen, of N. japonica was derived from upland plants in the upper estuary. In the lower estuary, a significant fraction of carbon of N. japonica was derived from phytoplankton. Notomastus sp. exhibited heavier δ 13C values than the surrounding surface sediment throughout the estuary and had heavier δ 13C values than N. japonica in the same location. These results suggest selective utilization of sedimentary carbon by those animals following bacterial processing and subsequent fractionation. The difference in δ 15N between sedimentary organics and corresponding polychaetes was 5 ± 1‰ and rather higher than 3.4 ± 1.1‰ expected for normal trophic effects in other animals.
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    Growth of the seaweed Ulva rigida C. Agardh in relation to biomass densities, internal nutrient pools and external nutrient supply in the Sacca di Goro lagoon (Northern Italy) (1996)
    Springer
    Hydrobiologia 329 (1996), S. 93-103 
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    ISSN: 1573-5117
    Keywords: Ulva rigida ; growth rates ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth of the seaweed Ulva rigida C. Agardh was investigated in relation to biomass densities, internal nutrient pools and external nutrient supply. Research was carried out from 23 March to 5 July 1994 in the Sacca di Goro (Po Delta, Northern Italy), whose south-eastern part was covered by extensive mats of Ulva rigida. Two types of field experiments were conducted by incubating Ulva thalli inside large cages. In the first experiment, beginning on 23 March, 100 g of wet thalli were placed into the cages, allowed to grow for two weeks, then collected and replaced. This procedure was repeated 8 times over the study period. In the second experiment, Ulva thalli were left inside the cages and collected at selected time intervals (14, 27, 41, 64 and 76 days) in order to simulate the effects of increased density on growth and nutrient storage. We recorded specific growth rates (NGR) ranging from 0.025 to 0.081 d−1 for a period up to two months in the repeated short-term experiments performed at relatively low initial algal densities (300–500 g AFDW m−3). These NGR resulted significantly related to dissolved inorganic nitrogen (DIN) in the water column. Tissue concentrations of total Kjeldahl nitrogen (TN) were almost constant, while extractable nitrate decreased in a similar manner to DIN in the water column. Total phosphorus showed considerable variation, probably linked to pulsed freshwater inflow. In the long-term incubation experiment, NGR of Ulva was inversely related to density. Internal concentrations of both total P and TN reached maximum values after one month; thereafter P concentration remained almost constant, while TN decreased below 2% w/w (by dry weight). The TN decrease was also accompanied by an abrupt decrease in nitrate tissue concentration. The biomass incubated over the two month period suffered a progressive N limitation as shown by a decreasing NY ratio (49.4 to 14.6). The reciprocal control of Ulva against biogeochemical environment and viceversa is a key factor in explaining both resource competition and successional stages in primary producer communities dominated by Ulva. However, when the biomass exceeds a critical threshold level, approximately 1 kg AFDW m−3, the macroalgal community switches from active production to rapid decomposition, probably as a result of selfshading, biomass density and development of anaerobic conditions within the macroalgal beds.
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    Oligochaetes and eutrophication; an experiment over four years in outdoor mesocosms (1996)
    Springer
    Hydrobiologia 334 (1996), S. 169-183 
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    ISSN: 1573-5117
    Keywords: Oligochaete ; eutrophication ; large-scale experiment ; ditch ; phosphorus ; nitrogen ; oxygen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Eight experimental ditch mesocosms were used to study the effect of eutrophication over four years. The experimental ditches had a sand or clay bottom. The ditches were treated with additions of phosphorus, phosphorus and nitrogen, or without additions (controls). Oligochaetes were sampled by deploying trays with substratum for colonization over twenty weeks. Both the important variables phosphorus, nitrogen and oxygen as well as the oligochaete species and numbers are presented. The effects of nutrient additions on phosphorus, nitrogen and oxygen concentrations were described together with changes in oligochaete species composition and numbers. The results were further analyzed by redundancy analysis (RDA). In the clay-lined ditches nutrient addition coincided with fluctuation in oxygen concentration. The higher the nutrient addition levels the longer the period of oxygen depletion became. During oxygen depletion the number of oligochaetes was strongly reduced or even became zero. The low nutrient status of the sandy bed in the sand-lined ditches slowed down the rate of colonization. Only a few tubificids were collected. Eutrophication effects were only observed at the highest nutrient addition level. Considerable variation is attributed to stochastic factors in the sand-lined ditches. Whether oligochaete species were present was related to the length of the colonization period. The substratum composition and food together with oxygen regime decided whether they become more or less abundant in ditches. Large-scale mesocosm experiments require time to develop. Only after the first colonization period variables of species presences and abundances can be employed to detect changes associated with eutrophication. Oligochaetes can be used to measure colonization as well as eutrophication processes.
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    Concentration of nutrients in selected lakes in the High Tatra Mountains, Slovakia: effect of season and watershed (1996)
    Springer
    Hydrobiologia 319 (1996), S. 47-55 
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    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; chlorophyll ; organic matter ; mountain lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Concentrations of total phosphorus (TP), inorganic and organic nitrogen, organic matter, and chlorophyll-a were studied in ten mountain lakes at various stages of acidification, trophy, and type of watershed during each July and October from 1987 to 1990. Concentrations of TP and total organic matter were higher in July than in October. Concentrations of NH44 +-N decreased and NO3 −-N increased from July to October. The relative composition of total nitrogen (TN) and its concentration were strongly dependent on the type of watershed: the lowest TN concentrations were observed in lakes with forested watersheds, increasing above the timberline and reaching maximum values in acidified lakes with rocky watersheds. In the pool of TN, nitrate was most important in lakes above the timberline (70–86% of TN), and organic nitrogen in forest lakes (〉 90% of TN). Lakes with rocky watersheds were characterized by high ratios of TN:TP (〉 250 by mass). The concentration of chlorophyll-a varied widely, from 0.01 to 22.6 µg l−1, without any consistent change between July and October, and were P limited.
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    Atmospheric deposition of sulphur, nitrogen and base cations in Scots pine stands of south-eastern Finland and the Karelian Isthmus, NW Russia in 1992 (1996)
    Springer
    Hydrobiologia 322 (1996), S. 223-226 
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    ISSN: 1573-5117
    Keywords: air pollution ; deposition ; sulphur ; nitrogen ; base cations ; throughfall ; Leningrad Region ; Scots pine ; soil water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper presents initial results of a joint Finnish-Russian investigation (1991–1996) of air pollutant deposition in Scots pine (Pinus sylvestris Linné) stands of Karelian Isthmus (north-western Leningrad Region, Russia) and south-eastern Finland. Bulk precipitation and canopy throughfall analyses revealed relatively high sulphur and nitrogen loads in the Karelian Isthmus and in the southern part of south-eastern Finland. The deposition load decreased gradually northwards, the highest levels of S and N deposition in the vicinity of St. Petersburg being two to three times higher than the values considered to be background level in Finland. Besides the acidifying elements, a high calcium deposition was detected in the Karelian Isthmus and in the southern part of south-eastern Finland. The high load of calcium, which probably emanates from oil shale burning in NE Estonia, alleviates the acidifying effect of sulphur and nitrogen deposition.
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    Water chemistry of Lake Ladoga and Russian-Finnish intercalibration of analyses (1996)
    Springer
    Hydrobiologia 322 (1996), S. 241-248 
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    ISSN: 1573-5117
    Keywords: water chemistry ; phosphorus ; nitrogen ; intercalibration ; Lake Ladoga ; large lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract As part of the Russian-Finnish research studies on Lake Ladoga, joint expeditions were organized in 1992 and 1993. Water samples were collected for intercalibration of chemical analysis methods and to monitor the chemical quality of the lake water. In August of 1992 water samples were taken from northern Lake Ladoga for intercalibration of Russian and Finnish analysis methods. In August 1993 water samples were collected from 23 sampling stations in all parts of the lake; some of these were also used for intercalibration purposes. The oxygen, colour and CODMn results were at the same level in the intercalibration. In 1993, the Ptot results obtained were acceptable. In Ntot, Fe and Mn analysis there seemed to be systematic and random errors between some results. The Secchi depth ranged from 1.5 m to 3.3 m. The average concentrations for the total phosphorus ranged from 15 µg 1−1 to 29 µg 1−1. The total nitrogen values were from 620 µg 1−1 to 690 µg 1−1. The N:P ratio varied from 24 to 40. The concentration of phosphorus indicated mesotrophic or even eutrophic conditions in the lake. Phosphorus seemed to be the limiting nutrient to bacteria and algae.
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    Use of an alternative method for monitoring total nitrogen concentrations in Florida lakes (1996)
    Springer
    Hydrobiologia 323 (1996), S. 1-8 
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    ISSN: 1573-5117
    Keywords: nitrogen ; water chemistry methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We studied a recently described method for the determination of total nitrogen in natural waters involving sample oxidation with persulfate and subsequent determination of nitrate-nitrogen with second derivative spectroscopy and compared it to the USEPA approved method involving the sum of nitrate-nitrogen and Kjeldahl-nitrogen as measured with an automated analyzer. The overall objective was to determine if the two methods gave the same estimates of total nitrogen and if the detection limits, precision and accuracy of the new method were as good as those of the USEPA method. The new method was used to make measurements on replicated blanks, standards and lake water samples covering a range of concentrations. We also collaborated with certified laboratories to make comparative measurements on 5 standards and 21 lake water samples that were run by us with the new method and by them with the USEPA method. The new method had an instrument detection limit of 0.07 mg 1−1, and the standard deviation of 20 sets of lake water samples averaged 0.03 mg 1−1. The new method gave concentrations equivalent to those found with the USEPA method, was more sensitive, and had a higher degree of precision. We concluded that the new method is suitable as a substitute for the USEPA method. We also found that the addition of acid to lake water samples stored under refrigeration was not necessary to preserve them for later determinations of nitrate-nitrogen and total nitrogen and that freezing was an effective means of sample preservation for 90 days.
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    Decomposition of Eucalyptus globulus leaves and three native leaf species (Alnus glutinosa, Castanea sativa and Quercus faginea) in a Portuguese low order stream (1996)
    Springer
    Hydrobiologia 333 (1996), S. 79-85 
    Details
    ISSN: 1573-5117
    Keywords: Leaf decomposition ; polyphenols ; nitrogen ; microbial colonization ; Eucalyptus globulus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf decomposition of the exotic evergreen Eucalyptus globulus (eucalyptus), and three native deciduous tree species, Alnus glutinosa (alder), Castanea sativa (chestnut) and Quercus faginea (oak), was compared in a second order stream in Central Portugal. Changes in dry weight, nitrogen and polyphenolic compounds and microbial colonization were periodically assessed for three months. Negative exponential curves fit the leaf weight loss with time for all leaf species. Mass loss rate was in the order alder (K = 0.0161) 〉 chestnut (K = 0.0079) 〉 eucalyptus (K = 0.0068) 〉 oak (K = 0.0037). Microbial colonization followed the same pattern as breakdown rates. Evidence of fungal colonization was observed in alder after 3 days in the stream, whereas it took 21 days in oak leaves to have fungal colonization. Fungal diversity was leaf species-dependent and increased with time. In all cases, percent nitrogen per unit leaf weight increased, at least, at the initial stages of decay while soluble polyphenolics (expressed as percentage per unit leaf weight) decreased rapidly in the first month of leaves immersion. Intrinsic factors such as nitrogen and polyphenolic content may explain differences in leaf decomposition. The possible incorporation of eucalyptus litter into secondary production in a reasonable time span is suggested, although community balance and structure might be affected by differences in allochthonous patterns determined by eucalyptus monocultures.
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    Ulva rigida (Ulvales, Chlorophyta) tank culture as biofilters for dissolved inorganic nitrogen from fishpond effluents (1996)
    Springer
    Hydrobiologia 326-327 (1996), S. 61-66 
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    ISSN: 1573-5117
    Keywords: biofilter ; nitrogen ; Sparus ; Ulvia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ulva rigida was cultivated in 7501 tanks at different densities with direct and continuous inflow (at 2, 4, 8 and 12 volumes d−1) of the effluents from a commercial marine fishpond (40 metric tonnes, Tm, of Sparus aurata, water exchange rate of 16 m3 Tm−1) in order to assess the maximum and optimum dissolved inorganic nitrogen (DIN) uptake rate and the annual stability of the ‘Ulva tank biofiltering system’. Maximum yields (40 g DW m−2 d−1) were obtained at a density of 2.5 g FW 1−1 and at a DIN inflow rate of 1.7 g DIN m−2 d−1. Maximum DIN uptake rates were obtained during summer (2.2 g DIN M−2 d−1), and minimum in winter (1.1 g DIN m−2 d−1) with a yearly average DIN uptake rate of 1.77 g DIN m−2 d−1 At yearly average DIN removal efficiency (2.0 g DIN m−2 d−1, if winter period is excluded), 153 m2 of Ulva tank surface would be needed to recover 100% of the DIN produced by 1 Tm of fish.
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    Do top-down and bottom-up controls interact to exclude nitrogen-fixing cyanobacteria from the plankton of estuaries? An exploration with a simulation model (1999)
    Springer
    Biogeochemistry 46 (1999), S. 203-231 
    Details
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; Zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by Zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high Zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a Zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
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    Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests (1999)
    Springer
    Biogeochemistry 46 (1999), S. 45-65 
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    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more 15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in 15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
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    URL: http://dx.doi.org/10.1023/A:1006100128782
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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    URL: http://dx.doi.org/10.1023/A:1006156213761
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    Do top-down and bottom-up controls interact to exclude nitrogen-fixing cyanobacteria from the plankton of estuaries? An exploration with a simulation model (1999)
    Springer
    Biogeochemistry 46 (1999), S. 203-231 
    Details
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
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    URL: http://dx.doi.org/10.1023/A:1006189121030
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  • 50
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    Subsurface horizontal-flow constructed wetlands for wastewater treatment: The Czech experience (1996)
    Springer
    Wetlands ecology and management 4 (1996), S. 199-206 
    Details
    ISSN: 1572-9834
    Keywords: constructed wetlands ; wastewater ; macrophytes ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The first full-scale constructed wetland (CW) in the Czech Republic was built in 1989 and there are now three tertiary systems and 50 secondary treatment facilities. We report here on the design and operational efficiencies of these facilities. All CWs have been designed with horizontal subsurface flow. Coarse sand, gravel and crushed stones with size fraction of 4–16 mm are commonly used as substrates. The area of vegetated beds ranges between 18 and 4500 m2 and operational CWs are designed for population equivalent (PE) of 4 to 1,100. Common reed (Phragmites australis) is the most frequently used macrophyte species. Results from systems studied during 1994 and 1995 show that the effluent concentrations of organics and suspended solids (SS) are well below the required discharge limits. In most cases the final effluent BOD5 concentration is 〈10 mg l−1. The relationship between vegetated bed BOD5 inflow loadings (L 0) and outflow loadings (L) is very strong (r=0.92). Constructed wetlands with subsurface horizontal flow usually do not remove larger amounts of nitrogen and phosphorus. The results from five Czech constructed wetlands show that nitrogen removal varies among systems, but the amount of removed nitrogen is very predictable. A regression equation between nitrogen inflow loading (L 0) and outflow loading (L) produces a strong correlation (r=0.98). The most important process responsible for phosphorus removal in wetlands is precipitation with soil Ca, Fe and Al. However, the subsurface horizontal flow constructed wetlands use mostly coarse gravel and/or sandy materials and this provides little or no P precipitation. Results from monitored systems in the Czech Republic show that the percentage phosphorus removal varies widely among systems and is lower than the percentage removal of organics and suspended solids.
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    URL: http://dx.doi.org/10.1007/BF01879238
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    A comparison of purification efficiencies of various constructed ecosystems (aquatic, semi-aquatic and terrestrial) receiving urban wastewaters (1996)
    Springer
    Wetlands ecology and management 4 (1996), S. 207-217 
    Details
    ISSN: 1572-9834
    Keywords: Alnus glutinosa ; constructed ecosystems ; disinfection ; Iris pseudacorus ; multi-stage systems ; nitrogen ; phosphorus ; constructed treatment wetlands ; optimization ; purification efficiencies ; urban wastewaters treatment ; Typha latifolia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tests were carried out under controlled conditions in the Experimental Plant of Viville (Arlon, Belgium) to enhance the purification of urban wastewater by “natural” means. The results demonstrate the need to structure treatment systems in a series of different artificial ecosystems (or a Hierarchical Mosaic of Artificial Ecosystems — MHEA in French). The first two levels we used were made up of an unplanted aquatic ecosystem (stabilization pond) followed by a semi-aquatic ecosystem planted withTypha latifolia L. in which the water flows over the substrate. At a flow rate of 4 m2/PE (1 PE=150 1/day of typical urban wastewaters in Belgian rural zones), this first stage substantially reduces suspended solids (SS), COD and BOD5, a significant amount of tot-N and tot-P, and reduces pathogens by 100-fold. Further, the system is easy to manage (sludge is eliminated in the first stage and biomass is collected in the second stage) and the treatment system does not clog up. Nevertheless, real and sustainable environmental protection demands even higher performance rates, and these first two stages, both in terms of design and dimension, can only be considered as a satisfactory part of a MHEA system. Artificial aquatic, semi-aquatic, and terrestrial ecosystems were systematically compared at the third and fourth stage of the system to increase the overall removal efficiency. The most complete and efficient system in our tests (i.e., the one that provides the most successful primary (SS), secondary (COD and BOD5) and tertiary (N and P) treatment and the best pathogens removal rates) was made up of 3 sequential series of ecosystems: an aquatic ecosystem whose flow went into a plantedTypha latifolia system (surface water flow), that flowed into a terrestrial ecosystem planted withAlnus glutinosa (L.) Gaertn (vertical subsurface water flow). A total surface area (stages 1–4) of 8 m2/PE ensured a high performance level whose outflow conformed to the strictest European norms.
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    URL: http://dx.doi.org/10.1007/BF01879239
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    Soil chemical limitations to growth and development of Veronica officinalis L. and Carex pilulifera L. (1996)
    Springer
    Plant and soil 184 (1996), S. 281-289 
    Details
    ISSN: 1573-5036
    Keywords: chlorosis ; growth ; iron ; nitrogen ; phosphate ; soil acidity ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Veronica officinalis and Carex pilulifera, widespread plants of acid soils in Europe, were grown in 50 soils of natural and seminatural ecosystems representing a wide range of soil chemical properties. The experiment was performed in a greenhouse at a soil moisture content of 55–65% WHC, ca. 60% R.H. of the air, temperature 14–16°C at night and 19–21°C by day; additional light 70 W m-2 12 h d-1. Properties closely related to soil acidity precluded growth of V. officinalis and limited the growth rate of C. pilulifera at soil pH-KCl 〈 ca. 3.4. In slightly-moderately alkaline (calcareous) soils, growth was primarily limited by insufficient phosphate uptake. A low growth rate of C. pilulifera. in such soils was related to low concentrations of exchangeable soil phosphate and low tissue concentrations of phosphorus. However, in high-pH soils, secondary effects due to suboptimum trace element (probably Fe) conditions, giving rise to symptoms of chlorosis, were also indicated. The highest growth rates of both species were invariably measured in soils of intermediate acidity having very high concentrations of exchangeable phosphate. Multiple regression tests on the entire material indicated that 65–75% of the variability in several growth functions could be accounted for, when two or more soil characters were included in the equation. Besides phosphate, exchangeable Zn (in C. pilulifera) and nitrate (in V. officinalis) were of considerable importance in accounting for growth rates.
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    URL: http://dx.doi.org/10.1007/BF00010457
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    The effect of soil desiccation on the nutrient status of Eucalyptus regnans F. Muell seedlings (1996)
    Springer
    Plant and soil 179 (1996), S. 45-56 
    Details
    ISSN: 1573-5036
    Keywords: Eucalyptus regnans ; nitrogen ; phosphorus ; soil desiccation ; soil microfractures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The poor growth of young Eucalyptus regnans seedlings in undried soil from the mature forest of E. regnans can be overcome by previously air-drying the soil or by adding sufficient amounts of complete soluble fertilizer or equivalent concentrations of P (as NaH2PO4) and N (as NaNO3). A factorial pot experiment in which phosphate and nitrate were added to undried soil indicated that P was the primary deficiency for young seedlings and that response to N did not occur until this lack was satisfied. In dried soil, seedlings also responded to additions of complete fertilizer but most of this effect was due to N rather than P. Field trials in the mature forest also indicated greater growth in dried soil than undried soil and confirmed a response of young seedlings to superphosphate. In pot experiments, the concentration of P and N per g plant dry weight after four months was relatively constant irrespective of the final size of the plant. Seedlings in dried soil extracted up to 15 times more P than did those grown in undried soil. In general, chemical analysis of soil indicated more extractable P and N from dried soil although this was not always consistently so. Soil desiccation resulted in an increase in soil surface area due to the fragmentation of larger peds and to an increase in the number of microfractures which remained in the soil crumbs after rewetting. Mycorrhiza are likely to be important since the differentiation of the growth response of seedlings in dried and undried soil, which occurred at 5–6 weeks, corresponded with the establishment of full ectomycorrhizal development (80% root tips). The factors concerned with the increase in fertility after air-drying are discussed.
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    URL: http://dx.doi.org/10.1007/BF00011641
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    Turnover of organic nitrogen in soils and its availability to crops (1996)
    Springer
    Plant and soil 181 (1996), S. 83-93 
    Details
    ISSN: 1573-5036
    Keywords: amino sugars ; fixed NH4 + ; immobilization ; mineralization ; nitrogen ; proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Major known fractions of soil nitrogen are amino nitrogen (proteins, peptides), polymers of amino sugars, and NH4 + fixed in interlayers of 2:1 minerals. Only a small percentage of the total soil organic N is easily mineralizable and contributes to the pool of mineral soil N. Predominant sources of mineralization are amino-N and polymers of amino sugars present in the soil microbial biomass. Influx into this pool occurs with the application of organic matter (green manure, straw), organic carbon released by plant roots, N2 assimilation by leguminous species and inorganic nitrogen. Microbial metabolization of green manure proteins results in a partial mineralization of the applied organic N, microbial metabolization of straw in the assimilation (immobilization) of inorganic nitrogen. Microbial biomass is characterized by a narrow C/N ratio (proteins, peptidoglycans, polymers of amino sugars). Its metabolization therefore is associated with a partial mineralization of the attacked organic nitrogen compounds. Nitrogen mineralization consists of a sequence of enzymatic processes for which the living microbial biomass provides the enzymes and the dead microbial biomass the substrate.
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    URL: http://dx.doi.org/10.1007/BF00011295
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    Effects of varied soil nitrogen supply on Norway spruce (Picea abies [L.] Karst.) (1996)
    Springer
    Plant and soil 186 (1996), S. 361-369 
    Details
    ISSN: 1573-5036
    Keywords: ectomycorrhiza ; fungus-specific compounds ; isocitrate dehydrogenase ; nitrogen ; Picea abies ; phosphoenolpyruvate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The response of carbohydrate metabolism in 3-year-old Norway spruce plants to an increased amount of nitrogen supply to a N-poor forest soil was investigated in a pot experiment. After 7 months of treatment we found a decreased amount of starch in both needles and roots, together with decreased amounts of sucrose in needles of those plants grown under an enhanced inorganic N supply. In addition, the activity and the protein amount of the anaplerotic enzyme phosphoenolpyruvate carboxylase (PEPC) and the activity of NADP-dependent isocitrate dehydrogenase (IDH) were clearly increased. The activity of sucrose phosphate synthase (SPS) and the pool size of fructose 2,6-bisphosphate (F26BP) were not affected by high supply of inorganic N. These data indicate a shift of carbon flow from starch formation towards an enhanced provision of carbon skeletons for N assimilation and shoot growth. In parallel, we found decreased contents of fungus-specific compounds (ergosterol, mannitol, trehalose) in roots, which are indicators of a decreased colonization by ectomycorrhizal fungi, probably as a result of a changed allocation and partitioning of photoassimilates due to an increased N supply.
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    URL: http://dx.doi.org/10.1007/BF02415531
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    The effect of regeneration burns on the growth, nutrient acquisition and mycorrhizae of Eucalyptus regnans F. Muell. (mountain ash) seedlings (1999)
    Springer
    Plant and soil 210 (1999), S. 273-283 
    Details
    ISSN: 1573-5036
    Keywords: ectomycorrhizae ; Eucalyptus regnans ; forest burns ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to compare the effects on the growth of Eucalyptus regnans seedlings of unheated soil and soil heated to different extents (as indicated by soil colour–bright red or black) in burnt logging coupes, and to separate the effects of heating of the soil on direct nutrient availability and on morphotypes and effectiveness of ectomycorrhizae. Burnt soils were collected from three logging coupes burnt 2, 14 and 25 months previously and unbumt soil from adjacent regrowth forests. Compared to unburnt soil, the early seedling growth was stimulated in black burnt soil from all coupes (burnt 2, 14 and 25 months previously). Seedling growth was generally poor in red burnt soil, especially in soil collected 2 months after burning. However, the concentration of extractable P was extremely high in red burnt soil, especially in soil collected 2 months after burning. In black burnt soil, extractable P was increased in soil 2 months after burning, but not in the soils collected 14 or 25 months after burning. However, both total P content and concentration in seedlings were increased in all collections of black burnt soil. Frequency of ectomycorrhizae was high in seedlings grown in all black burnt soils, but the mycorrhizal mantles were poorly developed in seedlings in black burnt soil collected 2 months after burning. Seedlings were also ectomycorrhizal in red burnt soil, except in soil collected 2 months after burning. Fine root inocula from seedlings grown in black burnt soils collected 14 and 25 months after burning significantly stimulated both seedling growth and P uptake compared with the uninoculated control, whereas the fine root inocula from the seedlings grown in all the other soils did not. These results suggest that, in black burnt soil, both direct nutritional changes and changes in the ectomycorrhizae may contribute to seedling growth promotion after regeneration burns. The generally poor seedling growth in red burnt soils is likely to have been due to N deficiency as the seedlings in these soils were yellow-green and the tissue concentrations of N were significantly lower than in other treatments.
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    URL: http://dx.doi.org/10.1023/A:1004609912315
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    Root, shoot and soil parameters required for process-oriented models of crop growth limited by water or nutrients (1996)
    Springer
    Plant and soil 183 (1996), S. 1-25 
    Details
    ISSN: 1573-5036
    Keywords: diffusion ; models ; nitrogen ; nutrient uptake ; phosphorus process-oriented ; resource use ; rooted volume ; rooting density ; root parameters ; roots ; spatial distribution ; uptake models ; water uptake ; zero sink
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A review is given of the prospects for using process-oriented models of water and nutrient uptake in improving ‘integrated agriculture’. Government-imposed restrictions on the use of external inputs will increase the likelihood of (temporary) nutrient or water stress in crop production in NW Europe and thus a better understanding is required of shoot-root-soil interactions than presently available. In modelling nutrient and water uptake, three approaches are possible: 1) models-without-roots, based on empirically derived efficiency ratios for uptake of available resources, 2) models evaluating the uptake potential of root systems as actually found in the field and 3) models which also aim at a prediction of root development as influenced by interactions with environmental factors. For the second type of models the major underlying processes are known and research can concentrate on model refinement on the one hand and practical application on the other. The main parameters required for such models are discussed and examples are given of practical applications. For the third type of models quantification of processes known only qualitatively is urgently needed.
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    URL: http://dx.doi.org/10.1007/BF02185562
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    Drought-avoidant soybean germplasm maintains nitrogen-fixation capacity under water stress (1996)
    Springer
    Plant and soil 186 (1996), S. 39-43 
    Details
    ISSN: 1573-5036
    Keywords: acetylene reduction ; drought ; drought-avoidant germplasm ; Glycine max (L.) Merrill ; growth ; nitrogen ; assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Inoculated soybeans (Glycine max L. (Merrill)) were grown in controlled environments to evaluate the relationship between genotype and plant water status on nodule function, nitrogen assimilation, growth rates, and seed yield. Plants were grown under well-watered (WW) and water-stressed (WS) conditions during the linear pod-filling growth stage in sand culture using N-free nutrient solution. Dry matter and N accumulation were greater for the drought-adapted Plant Introduction 416937 (PI) than for ‘Forrest’, a commercially adapted genotype of similar phenology. These differences are attributed to: (i) more favorable internal water balance throughout the pod-filling period (higher total leaf water potential), (ii) higher photosynthetic function (more total leaf area and higher net carbon exchange rates), and (iii) stronger nodule function (larger nodule mass, greater specific and total nodule activity, and thus more nitrogen assimilation) for the PI than for Forrest. While Forrest out yielded the PI under WW conditions, the percentage reduction in seed mass per plant was less for the PI than for Forrest when both genotypes were exposed to desiccating conditions. The inference is that soybean germplasm with the capacity to maintain tissue turgidity, and thus leaf and nodule function, during reproductively-imposed desiccation may reduce the extent to which yield is compromised during drought. These findings have implications for the role of symbiotic nitrogen fixation in conserving yield under dry weather conditions.
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    A comparison of direct and indirect 15N isotope techniques for estimating crop N uptake from organic residues (1999)
    Springer
    Plant and soil 208 (1999), S. 259-270 
    Details
    ISSN: 1573-5036
    Keywords: crop residues ; isotope dilution ; 15N ; nitrogen ; organic matter ; pool substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Experiments were carried out to compare the direct approach for estimating crop N uptake from 15N labelled organic inputs, to two indirect approaches, 15N isotope dilution and A value. In the first experiment soils received 25, 50, 75, or 100 mg N kg soil−1 in the form of Casuarina equisitifolia residues in addition to ammonium sulphate fertiliser, to give a total of 100 mg N kg soil−1 added. This was a cross labelling design, thus two matching sets of treatments, were set up, identical in all but the position of the 15N label. Maize (Zea mays L.) plants were grown in the soils amended with residues for 11 weeks and N derived from residues (Ndfr) estimated using the A-value or the direct approach. The A-value approach appeared to significantly overestimate %Ndfr compared to the direct method. In the second experiment contrasting residues were added to soil, fababean (Vicia faba L. var. minor), alfalfa (Medicago sativa L.), soyabean fixing, (Glycine max (L.) Merrill), soyabean non-fixing, barley (Hordeum vulgare L.) and maize. This was also cross-labelling design, labelled and unlabelled residues were used. Maize plants were grown in these soils for 11 weeks and %Ndfr in the maize plants estimated using 15 N isotope dilution and the direct approach. The 15 N isotope dilution approach also overestimated %Ndfr compared to the direct method in this experiment. Pool substitution appeared to be responsible for the discrepancy between the direct and indirect techniques. It was concluded that 15N isotope dilution and A-value approaches as used in these experiments (i.e where residues and 15N label are added simultaneously) were not appropriate techniques for estimating N derived from organic residues in soils.
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    URL: http://dx.doi.org/10.1023/A:1004529711231
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    Timing of nitrogen uptake affects winter storage and spring remobilisation of nitrogen in nectarine (Prunus persica var. nectarina) trees (1999)
    Springer
    Plant and soil 211 (1999), S. 149-153 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; Prunus ; remobilisation ; storage ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two-year old nectarine trees (Prunus persica, Batsch, var. nectarina, cv. Starkredgold on GF305 rootstock) planted in pots each received five applications of 1.0 g 15N labelled urea either from mid May to mid July (early uptake) or from mid August to the beginning of October (late uptake). All trees were supplied with a corresponding amount of unlabelled urea when they did not receive the labelled N. In autumn, all abscised leaves were collected and during winter randomly selected trees were harvested and divided into main organs. The remaining trees were transplanted into similar pots filled with sand; they received no N fertiliser and were harvested in May to evaluate the remobilisation of N. Total N and 15N abundance were determined in each organ. Nectarine trees took up similar amounts of N in the 'early' and in the 'late' period; however, more labelled nitrogen was recovered in the perennial organs during the winter when trees received the labelled N in the 'late' than in the 'early' period. Some 73–80% of the N present in the dormant trees was stored in the roots, which contained almost twice the amount of labelled N taken up 'late' than that absorbed 'early'. Nitrogen for spring growth was remobilised predominantly from the roots and accounted for some 43–49% of the labelled N recovered in the tree during winter. Results suggest that the nitrogen taken up 'late' in the season is preferentially stored in roots and used by peach trees to sustain new growth the following spring.
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    URL: http://dx.doi.org/10.1023/A:1004698422522
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    Effects of sulphur nutrition on growth and nitrogen fixation of pea (Pisum sativum L.) (1999)
    Springer
    Plant and soil 212 (1999), S. 207-217 
    Details
    ISSN: 1573-5036
    Keywords: legume ; nitrogen ; N2-fixation ; pea ; sulphur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A S-deficient soil was used in pot experiments to investigate the effects of S addition on growth and N2-fixation in pea (Pisum sativum L.). Addition of 100 mg S pot−1 increased seed yield by more than 2-fold. Numbers of pods formed were the most sensitive yield component affected by S deficiency. Sulphur addition also increased the concentration of N in leaves and stems, and the total content of N in the shoots. The amounts of N fixed by pea were determined at four growth stages from stem elongation to maturity, using the 15N dilution technique. Sulphur addition doubled the amount of N fixed at all growth stages. In contrast, leaf chlorophyll content and shoot dry weight were increased significantly by S addition only after the flowering and pod fill stage, respectively. Pea roots were found to have high concentrations of S, reaching approximately 10 mg g−1 dry weight and being 2.6–4.4 times the S concentration in the shoots under S-sufficient conditions. These results suggest that roots/nodules of pea have a high demand for S, and that N2-fixation is very sensitive to S deficiency. The effects of S deficiency on pea growth were likely to be caused by the shortage of N, due to decreased N2-fixation.
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    URL: http://dx.doi.org/10.1023/A:1004618303445
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    Applications of mineral nutrients to heavily N-fertilized Scots pine trees: Effects on arginine and mineral nutrient concentrations (1996)
    Springer
    Plant and soil 184 (1996), S. 57-65 
    Details
    ISSN: 1573-5036
    Keywords: amino acids ; arginine ; fertilization ; mineral nutrients ; nitrogen ; nitrogen deposition ; Pinus sylvestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aim of the investigation was to study if improved nutrient status in Scots pine (Pinus sylvestris L) trees would be reflected in decreased concentrations of arginine in the needles. The studies trees had imbalanced mineral nutrient composition and elevated needle arginine concentrations caused by long-term fertilization with N. Concentrations of arginine and mineral nutrients in needles were followed over three consecutive years of additional fertilization with N alone or with P, K, Mg and micronutrients in combination with and without N. Analysis of needle mineral concentrations suggested that there were deficiencies only in K and Mg. The N concentration increased both in trees fertilized with N alone and in trees fertilized with N in combination with mineral nutrients. In the control treatment and in trees fertilized with mineral nutrients other than N the N concentration remained fairly constant. The highest Ca/N, K/N and P/N ratios were found in trees fertilized with mineral nutrients other than N while the lowest ratios were found in trees fertilized with N alone. Arginine concentrations in needles from trees fertilized with N alone remained at a high level throughout the experiment while arginine concentrations in trees given the other treatments decreased. The results show that the mineral nutrient balance can be improved with appropriate fertilization and that this improvement is reflected in decreasing arginine levels. Furthermore the study demonstrates that when N supply is reduced the arginine concentration also decreases also as an effect of reduced N supply per se. The study also indicates that arginine may be a better measure of the N status in pine trees than total N.
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    Modelling the change in soil organic C and N and the mineralization of N from soil in response to applications of slurry manure (1996)
    Springer
    Plant and soil 184 (1996), S. 185-194 
    Details
    ISSN: 1573-5036
    Keywords: manure ; mineralization ; modelling ; nitrogen ; organic matter ; slurry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A computer simulation model of the turnover of organic matter in soil was adapted to simulate the change in soil organic C and N contents of soil during several years following annual additions of farm slurry to maize fields. The model proved successful in estimating the build-up of both C and N in soil and the leaching of N to ground-water in response to applications of slurry ranging from 50 to 300 tons per hectare per year. The model was then used to estimate the build-up of organic matter in soil under crops of fodder maize that were grown using the excess of manure produced during the last 20 years in the Netherlands. The build-up of organic matter from these applications was estimated to lead to about 70 kg extra nitrogen mineralized ha-1 yr-1. As a result of legislation manure applications have decreased and are expected to decrease further in the immediate future. Calculations suggest that after 10 years of manure applied at rates no longer exceeding the amount needed to replace the phosphorus removed by crops, the extra mineralization of N will still be between 45 and 60 kg ha-1 yr-1. If manure applications cease altogether then the extra mineralization will be about 25–30 kg N ha-1 yr-1.
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    URL: http://dx.doi.org/10.1007/BF00010448
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    Effects of varied soil nitrogen supply on Norway spruce (Picea abies [L.] Karst.) (1996)
    Springer
    Plant and soil 184 (1996), S. 291-298 
    Details
    ISSN: 1573-5036
    Keywords: foliar nutrient contents ; nitrogen ; Picea abies ; root growth ; root morphology ; root/shoot ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During a seven-month period the effect of different nitrogen (N) availability in soil on growth and nutrient uptake was studied in three-year-old Norway spruce (Picea abies [L.] Karst.) trees. The plants were grown in pots on N-poor forest soil supplied with various amounts and forms (inorganic and organic) of N. Increasing supply of inorganic N (as NH4NO3) increased the formation of new shoots and shoot dry weight. The root/shoot dry weight ratio of new growth was drastically decreased from 1.6 in plants without N supply to 0.5 in plants supplied with high levels of NH4NO3. This decrease in root/shoot dry weight ratio was associated with distinct changes in root morphology in favour of shorter and thicker roots. The addition of keratin as organic N source did neither affect growth nor root morphology of the trees. The amount of N taken up by plants was closely related to the supply of inorganic N, and trees supplied with highest levels of NH4NO3 also had the highest N contents in the dry matter of needles and roots. In contrast, N contents in needles of trees grown without additional N, or with keratin supply, were in the deficiency range. Supply of NH4NO3 decreased the contents of phosphate (P) and potassium (K) and therefore markedly increased N/P and N/K ratios in the needles. On the other hand, the contents of calcium (Ca), magnesium (Mg), and manganese (Mn) in the needles were increased in the plants supplied with inorganic N, suggesting high soil availability and promotion of uptake of these divalent cations by high nitrate uptake. The observed effects on root/shoot dry weight ratio, root morphology, and mineral nutrient composition of the needles indicated that high inorganic N supply may increase above-ground productivity but at the same time decrease the tolerance of trees against soil-borne (e.g. deficiency of other mineral nutrients) stress factors.
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    URL: http://dx.doi.org/10.1007/BF00010458
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    Using calcium carbide with the acetylene inhibition technique to measure denitrification from a sprinkler irrigated vegetable crop (1996)
    Springer
    Plant and soil 179 (1996), S. 9-16 
    Details
    ISSN: 1573-5036
    Keywords: acetylene inhibition ; calcium carbide ; denitrification ; nitrogen ; vegetable production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The use of calcium carbide (CaC2) pellets as a source of acetylene (C2H2) for the C2H2 inhibition technique to measure denitrification in the field was examined in a sandy loam soil cropped to lettuce. CaC2 was used in combination with vented closed chambers. Three grams of 2–4 mm CaC2 pellets were inserted at 7 and 20 cm for raised beds, and 6 and 15 cm for furrows, in four holes located at right angles, 2.5 cm outside a 20 cm dia. chamber pushed 4 cm into the soil. Acetylene concentrations were determined in the centre of the chamber 1.0 and 4.0 hours after applying CaC2, in beds (two dates) and furrows (one date) at different depths to 20 and 15 cm, respectively, for beds and furrows. At soil matric potentials of ca. 0.01 and ca. 0.06 MPa, soil C2H2 concentrations were 〉1.0% (v/v) for all determinations. Weekly measurements of denitrification were made from a sprinkler irrigated lettuce crop for 8 weeks. Measurements were made 24 hours after irrigation and on one occasion 48 hours after. Measured mean rates of denitrification were generally 〈100 g N ha−1 d−1, much less than published data following furrow irrigation of vegetable crops in a nearby region. In another sandy loam soil at ca. 0.08 MPa, soil C2H2 concentrations were ≥2.0 % at 5 and 15 cm, 1.0 and 6.0 hours after adding CaC2. Using CaC2 to generate C2H2 in soil is a convenient approach for field measurements where the C2H2 inhibition technique is used with chambers to determine the nitrous oxide flux. In comparison with C2H2 supply via probe systems, CaC2 overcomes the requirements for cylinders of pressurised C2H2 gas and complex on-site plumbing.
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    URL: http://dx.doi.org/10.1007/BF00011637
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    Enhancement of short-term nitrogen uptake by greenhouse roses under intermittent N-deprivation (1996)
    Springer
    Plant and soil 179 (1996), S. 73-79 
    Details
    ISSN: 1573-5036
    Keywords: deprivation ; intermitten ; nitrogen ; roses ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A recirculating nutrient solution system was utilized to study the effect of intermittent N deprivation on N uptake by mature ‘Royalty’ rose over the course of one flowering cycle. Plants received a nutrient solution lacking N for 4, 8 or 16 days, after which one containing NO3−N (0.75 mM) was supplied for 4 days. N-deprivation resulted in a 2–3 fold increase in N uptake rate compared to control plants supplied continuously with N. The magnitude of this deprivation-enhanced N uptake was not affected by either the duration of N-deprivation or the plant developmental stage. Over the course of the flowering cycle, the total cumulative N uptake by the plants was 95, 66, and 44% of the control plants in the 4, 8 and 16-day deprivation treatments, respectively. A characteristic diurnal pattern of N uptake occurred in both N-starved and control plants. Uptake oscillated between minimum rates in the morning and maximum rates in the evening, the latter occurring 4–6 hr after the maximum rate of transpiration.
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    URL: http://dx.doi.org/10.1007/BF00011644
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    Measuring and modelling nitrogen leaching: parallel problems (1996)
    Springer
    Plant and soil 181 (1996), S. 1-6 
    Details
    ISSN: 1573-5036
    Keywords: leaching ; nitrate ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In studies of nitrate leaching both experimenters and modellers experience problems arising from soil variability. Because of the small-scale heterogeneity that gives rise to mobile and immobile categories of water, both measurements and modelling are easiest in homogeneous sandy soils and most difficult in strongly structured clay soils. There are also parallels at plot and field scale in the problems caused to experimenters by log-normal distributions of nitrate concentrations and those caused to modellers by non-linearity in models. All researchers need to be aware that a reliable estimate of the mean from a set of measurements or a model may necessitate considerations of variances as well as means.
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    URL: http://dx.doi.org/10.1007/BF00011284
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    Nitrogen inputs and losses from New Zealand dairy farmlets, as affected by nitrogen fertilizer application: year one (1996)
    Springer
    Plant and soil 181 (1996), S. 65-69 
    Details
    ISSN: 1573-5036
    Keywords: ammonia volatilization ; denitrification ; grazed pasture ; leaching ; nitrogen ; N2 fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Inputs and losses of nitrogen (N) were determined in dairy cow farmlets receiving 0, 225 or 360 kg N ha-1 (in split applications as urea) in the first year of a large grazing experiment near Hamilton, New Zealand. Cows grazed perennial ryegrass/white clover pastures all year round on a free-draining soil. N2 fixation was estimated (using 15N dilution) to be 212, 165 and 74 kg N ha-1 yr-1 in the 0, 225 and 360 N treatments, respectively. The intermediate N rate had little effect on clover growth during spring but favoured more total pasture cover in summer and autumn, thereby reducing overgrazing and resulting in 140% more clover growth during the latter period. Removal of N in milk was 76,89 and 92 kg N ha-1 in the 0, 225 and 360 N treatments, respectively. Denitrification losses were low (7–14 kg N ha-1 yr-1), increased with N application, and occurred predominantly during winter. Ammonia volatilization was estimated by micrometeorological mass balance at 15, 45 and 63 kg N ha-1 yr-1 in the 0, 225 and 360 N treatments, respectively. Most of the increase in ammonia loss was attributed to direct loss after application of the urea fertilizer. Leaching of nitrate was estimated (using ceramic cup samplers at 1 m soil depth, in conjunction with lysimeters) to be 13, 18 and 31 kg N ha-1 yr-1 in a year of relatively low rainfall (990 mm yr-1) and drainage (170–210 mm yr-1). Drainage was lower in the N fertilized treatments and this was attributed to enhanced evapotranspiration associated with increased grass growth. Nitrate-N concentrations in leachates increased gradually over time to 30 mg L-1 in the 360 N treatment whereas there was little temporal variation evident in the 0 (mean 6.4 mg L-1) and 225 (mean 10.1 mg L-1) N treatments. Thus, the 360 N treatment had a major effect by greatly reducing N2 fixation and increasing N losses, whereas the 225 N treatment had little effect on N2 fixation or on nitrate leaching. However, these results refer to the first year of the experiment and further measurements over time will determine the longer-term effects of these treatments on N inputs, transformations and losses.
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    URL: http://dx.doi.org/10.1007/BF00011293
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    Temporal patterns of soil nutrients in a Panamanian moist forest revealed by ion-exchange resin and experimental irrigation (1996)
    Springer
    Plant and soil 183 (1996), S. 117-129 
    Details
    ISSN: 1573-5036
    Keywords: Barro Colorado Island ; base cations ; nitrogen ; phosphorus ; seasonal variation ; semideciduous forest ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of seasonal water availability on soil nutrients and soil N transformations was investigated by irrigating two large plots of mature tropical forest on Barro Colorado Island (BCI), Panama, during the dry season for five consecutive years. Methods included (i) nutrient accumulation by ion-exchange resins placed on the surface of the mineral soil for contiguous 21-day periods, (ii) monthly mineral soil (0–10 cm) extractions and incubations for inorganic N and P concentrations, and (iii) leaching loss of nutrients from leaf litter samples. Rates of nutrient accumulation by the resins showed a great deal of variation between sampling dates and among years in control plots; albeit, seasonal patterns were slight, except for the highest Ca values near the end of the wet season and inorganic P (Pi) and SO4 values that peaked during the dry season. Irrigation had remarkably little effect on nutrient accumulation rates by resins, except for an increase in Mg and Na values, but did affect the timing in the temporal variation in K, Na, Ni and Pi values. In contrast, inorganic N (Ni) and Pi pools and N transformation rates in the mineral soil hardly varied among sampling dates and did not show any response to irrigation. We hypothesize that the timing of leaf litterfall and nutrient leaching from forest floor litter can set up temporal patterns in the levels of soil nutrient at the surface of the mineral soil, but the temporal patterns essentially disappear with depth in the mineral soil.
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    URL: http://dx.doi.org/10.1007/BF02185571
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    The fate of fresh and stored 15N-labelled sheep urine and urea applied to a sandy and a sandy loam soil using different application strategies (1996)
    Springer
    Plant and soil 183 (1996), S. 213-220 
    Details
    ISSN: 1573-5036
    Keywords: ammonia volatilization ; animal manure ; N immobilization ; N mineralization ; N-balance ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The fate of nitrogen from 15N-labelled sheep urine and urea applied to two soils was studied under field conditions. Labelled and stored urine equivalent to 204 kg N ha−1 was either incorporated in soil or applied to the soil surface prior to sowing of Italian ryegrass (Lolium multiflorum L.), or it was applied to ryegrass one month after sowing. In a sandy loam soil, 62% of the incorporated urine N and 78% of the incorporated urea N was recovered in three cuts of herbage after 5 months. In a sandy soil, 51–53% of the labelled N was recovered in the herbage and the distribution of labelled N in plant and soil was not significantly different for incorporated urine and urea. Almost all the supplied labelled N was accounted for in soil and herbage in the sandy loam soil, whereas 33–34% of the labelled N was unaccounted for in the sandy soil. When the stored urine was applied to the soil surface, 20–24% less labelled N was recovered in herbage plus soil compared to the treatments where urine or urea were incorporated, irrespective of soil type. After a simulated urination on grass, 69% of the labelled urine N was recovered in herbage and 15% of the labelled N was unaccounted for. The labelled N unaccounted for was probably mainly lost by ammonia volatilization. Significantly more urine- than urea-derived N (36 and 19%, respectively) was immobilized in the sandy loam soil, whereas the immobilization of N from urea and urine was similar in the sandy soil (13–16%). The distribution of urine N, whether incorporated or applied to the soil surface prior to sowing, did not influence the immobilization of labelled urine N in soil. The immobilization of urine-derived N was also similar whether the urine was applied alone or in an animal slurry consisting of labelled urine and unlabelled faecal N. When urine was applied to growing ryegrass at the sandy loam soil, the immobilization of urine-derived N was significantly reduced compared to application prior to sowing. The results indicated that the net mineralization of urine N was similar to that of urea in the sandy soil, but only about 75% of the urine N was net mineralized in the sandy loam soil, when urine was applied prior to sowing. Thus, the fertilizer effect of urine N may be significantly lower than that of urea N on fine-textured soils, even when gaseous losses of urine N are negligible.
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    URL: http://dx.doi.org/10.1007/BF00011436
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    Persistence of tree related patterns in soil nutrients following slash-and-burn disturbance in the tropics (1999)
    Springer
    Plant and soil 209 (1999), S. 137-157 
    Details
    ISSN: 1573-5036
    Keywords: fire ; nitrogen ; phosphorus ; soil nutrient heterogeneity ; tree effects ; tropical dry forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO3 -), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO3 -, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils.
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    URL: http://dx.doi.org/10.1023/A:1004503023973
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    Nitrogen and phosphorus requirement of the microbiota in soils of the Bornhöved Lake district (1999)
    Springer
    Plant and soil 212 (1999), S. 173-181 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphatase activity ; phosphorus ; protease activity ; soil microbial biomass ; substrate-induced respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Estimating in situ N and P status of the soil microbiota is complicated because microbiological features reflect potentials rather than field conditions. Complementary microbiological assays were, therefore, combined to evaluate the N and P requirement of the microbiota in seven agricultural, grassland and forest topsoils of the Bornhöved Lake district as follows: (i) the sensitivity of the substrate-induced respiration (SIR) to supplemental addition of N and P was monitored during microbial growth and (ii) soil protease and phosphatase activities were analysed and related to soil mass and microbial biomass content. Nitrogen addition increased the maximal SIR rate in all except one soil indicating that the growth of organisms is restricted by this element when easily degradable C source is present. Supplemental N (and in some cases also P) retarded the respiratory response within the first 24 h which suggests microbial sensitivity and/or greater anabolic efficiency. With additional N the maximal SIR rate was most strongly enhanced in topsoils of the beech forest and the dystric alder forest. Thus, the microbial growth in these soils that were below litter horizons seems to be mostly restricted by N. Supplemental P positively affected respiratory response of soils under monoculture, wet grassland and dystric alder forest. In the dystric alder forest soil, high rates of alkaline and unbuffered phosphatase activity were observed when activity was related to either soil mass or microbial biomass content. The data of proteolytic and phospholytic enzymes are discussed with reference to nutrient deficiency and microbial strategy for N and P adsorption.
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    URL: http://dx.doi.org/10.1023/A:1004677427165
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    Contributions to nitrogen leaching and pasture uptake by autumn-applied dairy effluent and ammonium fertilizer labeled with 15N isotope (1999)
    Springer
    Plant and soil 210 (1999), S. 189-198 
    Details
    ISSN: 1573-5036
    Keywords: effluent ; leaching ; 15N isotope ; nitrogen ; pasture ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this study was to compare the N leaching loss and pasture N uptake from autumn-applied dairy shed effluent and ammonium fertilizer (NH4Cl) labeled with 15N, using intact soil lysimeters (80 cm diameter, 120 cm depth). The soil used was a sandy loam, and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The DSE and NH4Cl were applied twice annually in autumn (May) and late spring (November), each at 200 kg N ha-1. The N applied in May 1996 was labeled with 15N. The lysimeters were either spray or flood irrigated during the summer. The autumn-applied DSE resulted in lower N leaching losses compared with NH4Cl. However, the N applied in the autumn had a higher potential for leaching than N applied in late spring. Between 4.5–8.1% of the 15N-labeled mineral N in the DSE and 15.1–18.8% of the 15N-labeled NH4Cl applied in the autumn were leached within a year of application. Of the annual N leaching losses in the DSE treatments (16.0–26.9 kg N ha-1), a fifth (20.3–22.9%) was from the mineral N fraction of the DSE applied in the autumn, with the remaining larger proportion from the organic fraction of the DSE, soil N and N applied in spring. In the NH4Cl treatments, more than half (53.8–64.8%) of the annual N leaching loss (55.9–57.6 kg N ha-1) was derived from the autumn-applied NH4Cl. DSE was as effective as NH4Cl in stimulating pasture production. Since only 4.4–4.5% of the annual herbage N uptake in the DSE treatment and 12.3–13.3% in the NH4Cl treatment were derived from the autumn-applied mineral N, large proportions of the annual herbage N uptake must have been derived from the N applied in spring, the organic N fraction in the DSE, soil N and N fixed by clover. The recoveries of 15N in the herbage were similar between the DSE and the NH4Cl treatments, but those in the leachate were over 50% less from the DSE than from the NH4Cl treatment. The lower leaching loss of 15N in the DSE treatment was attributed to the stimulated microbial activities and increased immobilization following the application of DSE.
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    Nitrogen compounds and phosphate of the Driss I reservoir (Morocco): input, output and sedimentation (1996)
    Springer
    Hydrobiologia 335 (1996), S. 75-82 
    Details
    ISSN: 1573-5117
    Keywords: reservoir ; phosphate ; nitrogen ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to study the N and P balances in the Driss I reservoir, we measured concentrations in the water of these elements, their sedimentation rates, and their input by the river Inaouen and output through the dam. Supply and loss of N and P were calculated from samples collected every 48 hours and were for N 15 and 27. 5 mg m−2 d−1 and for P 33.6 and 1.1 mg m−2 d−1 respectively. The sedimentation rates, determined using sediment traps, were high, about 75 mg m−2 d−1 for N and 34 mg m−2 d−1 for P. Phosphate input came from point sources and was mainly in particulate form. A large fraction of the phosphate sedimented in the form of calcium bound phosphate, with some iron bound phosphate. Bioavailability was, however, low, as the particulate phosphate disappeared rapidly from the epilimnion because of the high sedimentation rate. The ratio Tot-N/Tot-P of the sedimented particulate matter varied between 0.05 and 7.74 and depended on primary production and watergate management.
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    URL: http://dx.doi.org/10.1007/BF00013685
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    Variations in mineral nitrogen levels: the River Adour (1996)
    Springer
    Hydrobiologia 335 (1996), S. 159-170 
    Details
    ISSN: 1573-5117
    Keywords: denitrification ; mineral ; nitrogen ; Adour ; mineralisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A section of the River Adour (SW France) has been investigated to determine the role of the riparian vegetative strips (rvs) in the retention of mineral nitrogen. Entering and exiting fluxes have been measured along this segment throughout a hydrological season. The study indicates gains in mineral nitrogen (∼ 28%) during periods of low flow in the summer months, with riparian vegetation utilising 2.3 to 3.7% of the entering flux. Significant losses (∼ 50%) of nitrogen are observed in autumn, whereas minor losses are observed during the two flood events of November 1991 and June 1992 (4.6 – 4.9% of the entering flux). In winter losses of mineral nitrogen due to denitrification are small varying from 0.07% in winter, to 7% in summer, of the entering flux. The input of dissolved nitrogen through rainfall is estimated to be negligible within the zone studied. Additions of fertiliser for maize cultivation in February, May, June and July of 1992 have a significant impact on the fluxes exiting, the study zone. In May, the added nitrogen is used largely in the growth of the maize, what remains is is retained in the riparian vegetation. By contrast, in June, 27.2% of the available nitrogen added as fertiliser is found in the river. Finally, during the course of the hydrological year an increase in mineral nitrogen of 519 tonnes is observed in the area studied between Pontonx and Dax, of which only 224.8 tonnes can be ascribed to the addition of fertiliser. The remainder of this enrichment is explained by mineralisation of organic nitrogen stored in the riparian vegetative strips.
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    URL: http://dx.doi.org/10.1007/BF00018983
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    Relationships between eutrophication variables: from nutrient loading to transparency (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 375-387 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; multi-lake studies ; phosphorus ; nitrogen ; chlorophyll-a ; transparency ; zooplankton ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring data obtained from 231 freshwater lakes and ponds in the Netherlands, covering the period 1980–1996, were used to analyse the relationships between (a) transparency and chlorophyll-a, and the effect of system characteristics on this relationship, (b) chlorophyll-aand nutrient concentrations, and the effect of biological variables and (c) nutrient concentrations and nutrient loading. (a) Chlorophyll-aimposes a maximum on water transparency, but deviations from this maximum can be large. Reducing chlorophyll-a, therefore, does not guarantee a sufficient improvement of transparency. Soil type and the average depth of a lake were shown to influence the relationship between chlorophyll-aand transparency. (b) The maximum ratios of both chlorophyll-a: total-P and chlorophyll-a: total-N were higher in systems dominated by filamentous cyanobacteria than in systems dominated by other algae, indicating the efficiency of the former group with respect to nutrients. In systems with an areal coverage with submersed macrophytes above 5%, concentrations of chlorophyll-aand nutrients were lower than in systems with lower coverages. The ratios between chlorophyll-aand nutrients were lower at coverages larger than 10%. This indicates both bottom-up and top-down control of algae by macrophytes. Grazing pressure by zooplankton was also found to lower the chlorophyll-a: nutrient ratios. (c) System specific linear relationships were found between the average concentrations of total-P and total-N in the incoming water and the summer mean concentration in the lake. This allows the assessment of admissible loads for individual lakes, with narrower confidence limits compared to traditional relationships based on combined data from many lakes. From the analysis, it is concluded that the chain of relationships from nutrient loading to transparency is complex, and depends on biological variables as well as system characteristics.
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    URL: http://dx.doi.org/10.1023/A:1017090931476
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    Microbial activity under alpine snowpacks, Niwot Ridge, Colorado (1996)
    Springer
    Biogeochemistry 32 (1996), S. 93-113 
    Details
    ISSN: 1573-515X
    Keywords: alpine ; biogeochemistry ; nitrogen ; nitrogen saturation ; snowmelt ; soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Experiments were conducted during 1993 at Niwot Ridge in the Colorado Front Range to determine if the insulating effect of winter snow cover allows soil microbial activity to significantly affect nitrogen inputs and outputs in alpine systems. Soil surface temperatures under seasonal snowpacks warmed from −14 °C in January to 0 °C by May 4th. Snowmelt began in mid-May and the sites were snow free by mid June. Heterotrophic microbial activity in snow-covered soils, measured as C02 production, was first identified on March 4, 1993. Net C02 flux increased from 55 mg CO2-C m−2 day−1 in early March to greater than 824 mg CO2-C m-2 day−1 by the middle of May. Carbon dioxide production decreased in late May as soils became saturated during snowmelt. Soil inorganic N concentrations increased before snowmelt, peaking between 101 and 276 mg kg−1 soil in May, and then decreasing as soils became saturated with melt water. Net N mineralization for the period of March 3 to May 4 ranged from 2.23 to 6.63 g N m−2, and were approximately two orders of magnitude greater than snowmelt inputs of 50.4 mg N m−2 for NH4 + and 97.2 mg N m−2 for NO3 −. Both NO3 − and NH4 + concentrations remained at or below detection limits in surface water during snowmelt, indicating the only export of inorganic N from the system was through gaseous losses. Nitrous oxide production under snow was first observed in early April. Production increased as soils warned, peaking at 75 μg N2O-N m−2 day−1 in soils saturated with melt water one week before the sites were snow free. These data suggest that microbial activity in snow-covered soils may play a key role in alpine N cycling before plants become active.
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    The origin and recycling of sedimented biogenic debris in a subalphine eutrophic lake (Lake Bled, Slovenia) (1996)
    Springer
    Biogeochemistry 32 (1996), S. 69-91 
    Details
    ISSN: 1573-515X
    Keywords: lacustrine sediment ; organic matter ; sedimentation rates ; recycling ; burial ; carbon ; nitrogen ; silicon ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The areal distribution of organic C contents, δ13C values, total N and P and biogenic Si contents in surficial sediments were used to study the distribution, origin and diagenetic transformations of sedimented biogenic debris in the eutrophic subalpine Lake Bled (Slovenia), which for most of the yearhas an anoxic hypolimnion. The influence of an allochthonous input, restricted to the western basin, was clearly traced by higher organic C and total N and P contents, higher δ13C values, and higher sedimentation rate in comparison to the eastern basin. The low δ13C values of sedimentary organic matter in the major part of the lake, lower than the δ13C values of different types of organic matter, suggest that this sedimentary organic matter is most probably the product of a microbial community and not a residue of primary production. The temporal variation of benthic diffusive fluxes of NH4, Si and PO4, derived from modelling the pore water profiles, was related to sedimentation of phytoplanktonic blooms, while the PO4 fluxes were also dependent on changing redox conditions at the sediment-water interface in the period of the winter-spring overtum. The removal of PO4 in pore waters is probably due to the adsorption of phosphate and precipitation of apatite and vivianite. The budget of C, N and P at the sediment-water interface revealed a high recycling efficiency (〉70%), also confirmed by the rather uniform (or only slightly decreasing) vertical profiles of organic C, total N and P in sediment cores and C/N and C/P ratios. The percentage of biogenic Si recycling is low (〈10%), suggesting its removal in sediments.
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  • 79
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    The fate of nitrogen and phosphorus at the land-sea margin of the North Atlantic Ocean (1996)
    Springer
    Biogeochemistry 35 (1996), S. 141-180 
    Details
    ISSN: 1573-515X
    Keywords: continental shelf ; estuaries ; mass balance ; nitrogen ; North Atlantic ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Five large rivers that discharge on the western North Atlantic continental shelf carry about 45% of the nitrogen (N) and 70% of the phosphorus (P) that others estimate to be the total flux of these elements from the entire North Atlantic watershed, including North, Central and South America, Europe, and Northwest Africa. We estimate that 61 · 109 moles y−1 of N and 20 · 109 moles y−1 of P from the large rivers are buried with sediments in their deltas, and that an equal amount of N and P from the large rivers is lost to the shelf through burial of river sediments that are deposited directly on the continental slope. The effective transport of active N and P from land to the shelf through the very large rivers is thus reduced to 292 · 109 moles y−1 of N and 13 · 109 moles y−1 of P. The remaining riverine fluxes from land must pass through estuaries. An analysis of annual total N and total P budgets for various estuaries around the North Atlantic revealed that the net fractional transport of these nutrients through estuaries to the continental shelf is inversely correlated with the log mean residence time of water in the system. This is consistent with numerous observations of nutrient retention and loss in temperate lakes. Denitrification is the major process responsible for removing N in most estuaries, and the fraction of total N input that is denitrified appears to be directly proportional to the log mean water residence time. In general, we estimate that estuarine processes retain and remove 30–65% of the total N and 10–55% of the total P that would otherwise pass into the coastal ocean. The resulting transport through estuaries to the shelf amounts to 172–335 · 109 moles y−1 of N and 11–19 · 109 moles y−1 of P. These values are similar to the effective contribution from the large rivers that discharge directly on the shelf. For the North Atlantic shelf as a whole, N fluxes from major rivers and estuaries exceed atmospheric deposition by a factor of 3.5–4.7, but this varies widely among regions of the shelf. For example, on the U.S. Atlantic shelf and on the northwest European shelf, atmospheric deposition of N may exceed estuarine exports. Denitrification in shelf sediments exceeds the combined N input from land and atmosphere by a factor of 1.4–2.2. This deficit must be met by a flux of N from the deeper ocean. Burial of organic matter fixed on the shelf removes only a small fraction of the total N and P input (2–12% of N from land and atmosphere; 1–17% of P), but it may be a significant loss for P in the North Sea and some other regions. The removal of N and P in fisheries landings is very small. The gross exchange of N and P between the shelf and the open ocean is much larger than inputs from land and, for the North Atlantic shelf as a whole, it may be much larger than the N and P removed through denitrification, burial, and fisheries. Overall, the North Atlantic continental shelf appears to remove some 700–950· 109 moles of N each year from the deep ocean and to transport somewhere between 18 and 30 · 109 moles of P to the open sea. If the N and P associated with riverine sediments deposited on the continental slope are included in the total balance, the net flux of N to the shelf is reduced by 60 · 109 moles y−1 and the P flux to the ocean is increased by 20 · 109 moles y−1. These conclusions are quite tentative, however, because of large uncertainties in our estimates of some important terms in the shelf mass balance.
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    URL: http://dx.doi.org/10.1007/BF00993000
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1× 104 kg nitrogen and 3.91×104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7×104 kg (676 kg/ha) nitrogen and 3.88×104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55×104 kg nitrogen and 0.40×104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    URL: http://dx.doi.org/10.1007/BF00992870
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    Nutrient losses in runoff from grassland and shrubland habitats in Southern New Mexico: I. rainfall simulation experiments (1999)
    Springer
    Biogeochemistry 45 (1999), S. 21-34 
    Details
    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/1) and lowest in bare plots in the shrubland (0.55 mg/1). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands — consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
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    URL: http://dx.doi.org/10.1007/BF00992871
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    Pore water N and P concentration in a floodplain marsh of the Lower Paraná River* (1999)
    Springer
    Hydrobiologia 392 (1999), S. 65-71 
    Details
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; pore water ; macrophyte ; floodplain ; Paraná River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water of a marsh and in its interstitial water at two sites, and in the river water of a floodplain marsh of the Lower Paraná River. These values were compared with the N and P concentration in sediments and macrophyte biomass in order to assess nutrient availability, fate and storage capacity. High variability was found in the interstitital water using a 1 cm resolution device. Nitrate was never detected in the pore water. Depth averaged NH4 + concentrations in the upper 30 cm layer often ranged from N = 1.5 to 1.8 mg l-1, but showed a pronounced minimum (0.5–0.7 mg l-1), close to (March 95), or relatively soon after (May 94) the end of the macrophyte growing season. Soluble phosphate showed a large variation between P = 0.1–1.1 mg l-1 without any discernible seasonal pattern. NH4 + depletion in the pore water concentration and low N/P ratios (3.7 by weight) within the macrophyte biomass at the end of the growing period suggest that available N limits plant growth. NH4 + and o-P concentrations were 35 and 7 times higher, respectively, in the pore water than in the overlying marsh, suggesting a permanent flux of nutrients from the sediments. o-P accumulate in the marsh leading to higher concentrations than in the incoming river. NH4 + did not accumulate in the marsh, and no significant differences were observed between the river and the marsh water, while the NO3 - contributed by the river water was depleted within the marsh, caused probably by coupled nitrification-denitrification at the sediment–water interface. Although an order of magnitude smaller, the pore water pool can supply enough nutrients to build up the macrophyte biomass pool, but only if a fast turnover is attained. The Paraná floodplain marsh retains a large amount of nutrients being stored mainly in the sediment compartment.
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    URL: http://dx.doi.org/10.1023/A:1003505424569
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    The N and P budget of the shallow, flushed lake Müggelsee: retention, external and internal load (1999)
    Springer
    Hydrobiologia 408-409 (1999), S. 159-166 
    Details
    ISSN: 1573-5117
    Keywords: shallow lake ; nutrient loading ; retention ; nitrogen ; phosphorus ; release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The shallow (mean depth 4.9 m), polymictic and eutrophic lake Müggelsee was highly loaded with phosphorus (6 gP m-2a-1) and nitrogen (170 gN m-2a-1) by the river Spree up to the end of the 1980s. Annual load declined by 40–50% during the last years (1991–97). Phosphorus retention fluctuated strongly during the seasonal cycle between −200 and +100 kgP d-1and from year to year between −44% and + 26% of the P import. At the end of the eighties, the P retention capacity of the sediment was exceeded and Müggelsee became a source of phosphorus. The lake regained its ability to retain P in the sediments after external load reduction in the 1990s. However, the internal load of P reached the level of the external one. The release of P during summer was strongly related to the import of nitrate. On long-term average (1979–1997), less than 1% of the P input was retained in Müggelsee. About 24% of the nitrogen load were removed in the lake on annual mean. This rate decreased during the last years.
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    Legislative challenges for lake eutrophication control in Europe (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 389-401 
    Details
    ISSN: 1573-5117
    Keywords: legislation ; eutrophication ; phosphorus ; nitrogen ; wildlife conservation ; SSSI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is no single piece of legislation which comprehensively addresses the problem of eutrophication of freshwater lakes. An examination is made of the extent to which national and EU laws applicable in England and Wales may be used to reduce phosphorus inputs to eutrophicated lakes. This case study is then used to outline the shortcomings of existing legislation and the future challenges for lake eutrophication control. Applicable legislation may be divided into that relating to nature conservation, to water quality and to agricultural extensification. Nature conservation laws are applicable, in that lakes designated as Sites of Special Scientific Interest (SSSIs), are theoretically safeguarded from degradation. The main limitation of the SSSI system lies in the boundary definition process under which, as a rule, no other category of legally protected land may be designated. Thus, the use of surrounding buffer land to protect water quality at the catchment level is generally precluded. The introduction of consultation areas around SSSIs of international importance under the EU Directive on Habitats is unlikely to alleviate the problem, since the area involved remains minimal compared to the extent of the majority of catchments. Intensive agricultural practices are responsible for significant nutrient enrichment of rivers and lakes, so that legislation aimed at extensification is also relevant. Examples of agricultural extensification include the Environrnentally Sensitive Areas programme and various options available for Set-Aside land. However, the prime purpose of such initiatives is the alleviation of surplus and budgetary problems and, as such, they fall short of a fully integrated approach to the ecological management of farmland. Nutrient enrichment is, essentially, a water quality issue, but policy and legislation in this area are not yet sufficiently developed to address the problem comprehensively. The current regulatory process for water quality carries the potential to work comparatively well for point sources under the system of consents to discharge. This potential is limited, however, by the paucity of information available on ecologically acceptable concentrations of phosphorus in discharges. In addition, the consents system is not constructed to deal effectively with diffuse agricultural losses of phosphorus, since, unlike point sources, these tend to arise from the cumulative effect of many activities. The main legislative challenge for lake eutrophication control lies in the area of diffuse agricultural losses of phosphorus. In this respect, experience in the U.S.A. reveals that the use of comprehensive and catchment-wide ‘Best Management Practices’ is capable of producing significant water quality improvements, providing that some degree of mandatory compliance is incorporated.
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    Lake and catchment management in Denmark (1999)
    Springer
    Hydrobiologia 395-396 (1999), S. 419-432 
    Details
    ISSN: 1573-5117
    Keywords: Integrated lake management ; biomanipulation ; lake recovery ; phosphorus ; nitrogen ; eutrophication ; restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The majority of Danish lakes are highly eutrophic due to high nutrient input from domestic sources and agricultural activities. Reduced nutrient retention, and more rapid removal, in catchments as a result of agricultural drainage of wetlands and lakes and channelisation or culverting of streams also play a role. Attempts have recently been made to reduce nutrient loading on lakes by intervening at the source level and by improving the retention capacity of catchment areas. The former measures include phosphorus stripping and nitrogen removal at sewage works, increased use of phosphate-free detergents, and regulations concerning animal fertiliser storage capacity, fertiliser application practices, fertilisation plans and green cover in winter. In order to improve nutrient retention capacity of catchments, wetlands and lakes have been re-established and channelised streams have been remeandered. In addition, cultivation-free buffer strips have been established alongside natural streams and there has been a switch to manual weed control. These measures have resulted in a 73% reduction of the mean total phosphorus concentration of point-source polluted streams since 1978; in contrast, there has been no significant change in the total nitrogen concentration. Despite the major reduction in stream phosphorus concentrations, lake water quality has often not improved. This may reflect a too high external or internal phosphorus loading or biological resistance. Various physico-chemical restoration measures have been used, including dredging and oxidation of the hypolimnion with nitrate and oxygen. Biological restoration measures have been employed in 17 Danish lakes. The methods include reducing the abundance of cyprinids, stocking with 0+ pike ( Esox lucius) to control 0+ cyprinids, and promoting macrophyte recolonization by protecting germinal submerged macrophyte beds against grazing waterfowl and transplanting out macrophyte shoots. In several lakes, marked and long-lasting improvements have been obtained. The findings to date indicate that fish manipulation has a long-term effect in shallow lakes, providing nutrient loading is reduced to a level so low as to ensure an equilibrium lake water phosphorus concentration of less than 0.05–0.1 mg phosphorus l−1. If nitrogen loading is very low, however, positive results may be obtained at higher phosphorus concentrations. Macrophyte refuges and transplantation seem to be the most successful as restoration measures in the same nutrient-phosphorus regime as fish manipulation.
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    URL: http://dx.doi.org/10.1023/A:1017071602549
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    A simulation model of organic matter and nutrient accumulation in mangrove wetland soils (1999)
    Springer
    Biogeochemistry 44 (1999), S. 93-118 
    Details
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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    Nutrient budgets and biogeochemistry in an experimental agricultural watershed in Southeastern China (1999)
    Springer
    Biogeochemistry 45 (1999), S. 1-19 
    Details
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1 × 104 kg nitrogen and 3.91 × 104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7 × 104 kg (676 kg/ha) nitrogen and 3.88 × 104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55 × 104 kg nitrogen and 0.40 × 104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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    The fate of NH4NO3 added toSphagnum magettanicum carpets at five European mire sites (1999)
    Springer
    Biogeochemistry 45 (1999), S. 73-93 
    Details
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m−2 yr−1 were made toSphagnum magellanicurn cores at two-week intervalsin situ at four sites across Europe, i.e. Lakkasuo (Finland). Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N∶P ratio 68) and greatest in Moidach More (N∶P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4 + in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3 − were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition bySphagnum mosses.
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    URL: http://dx.doi.org/10.1007/BF00992874
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    Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests (1999)
    Springer
    Biogeochemistry 46 (1999), S. 45-65 
    Details
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
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    URL: http://dx.doi.org/10.1007/BF01007573
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    The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes (1999)
    Springer
    Biogeochemistry 46 (1999), S. 109-148 
    Details
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01007576
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  • 92
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    ATP levels of chinook salmon (Oncorhynchus tshawytscha) sperm following in vitro exposure to various oxygen tensions (1999)
    Springer
    Fish physiology and biochemistry 20 (1999), S. 389-397 
    Details
    ISSN: 1573-5168
    Keywords: adenosine triphosphate ; fertility ; nitrogen ; salmonid ; semen ; spermatocrit ; viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adenosine triphosphate (ATP) levels in sperm from chinook salmon (Oncorhynchus tshawytscha) were found to be 12.1±1.9 pmol ATP per 106 sperm cells (mean±SEM, n=18). Sperm were stored at 0–2 °C for up to 72 h under 100, 21, and 0% O2. Changes in sperm ATP content of samples maintained under 100 and 21% O2 were indistinguishable, decreasing to 50% of initial values after 72 h. ATP levels of sperm stored under 0% O2 decreased to 10% of initial values within 8 h and remained unchanged throughout the following 64 h. The initial percent of living sperm (sperm viability) was 94.7±1.7% (mean±SEM, n=12) and was unaltered at 24 h under all O2 tensions. At 72 h, sperm viability remained unchanged under 21% O2 and had decreased by 20% under 100% O2 and by 30% under 0% O2. Therefore, reductions in sperm ATP levels could not be attributed to cell lysis, as viability decreased only modestly over these durations. Fertilizing ability correlated positively with sperm ATP levels. Spermatocrit values increased by 20% for the samples maintained under 100 and 21% O2 after 72 h. However, a 20% increase in spermatocrit occurred within 24 h in samples maintained under 0% O2, rising 70% after 72 h under 0% O2. These data indicate that chinook sperm ATP (1) can be altered and manipulated without significant loss of viability, (2) is positively associated with fertilization, and (3) probably plays a role in sperm packing and cell flexibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007749703803
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  • 93
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    Effect of soil characteristics on sequential reduction and methane production in sixteen rice paddy soils from China, the Philippines, and Italy (1999)
    Springer
    Biogeochemistry 47 (1999), S. 267-293 
    Details
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 - , SO 4 2 , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4 and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9 μmol d-1 g-1 dry soil. Methane production started after 2 to 87 days and became constant after about 38--68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08 μmol d-1 g-1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30 μmol d-1 g-1 and 0.02 and 0.28 μmol d-1 g-1, respectively. Within the 120 d of anaerobic incubation only 6--17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61--100% CO2, 〈0.1--35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r = 0.891) and total CH4 produced (r = 0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006186420644
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  • 94
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    Electronic Resource
    Effect of soil characteristics on sequential reduction and methane production in sixteen rice paddy soils from China, the Philippines, and Italy (1999)
    Springer
    Biogeochemistry 47 (1999), S. 269-295 
    Details
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 − , SO 4 2− , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4. and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9μmol d−1 g−1 dry soil. Methane production started after 2 to 87 days and became constant after about 38–68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08μmol d−1 g−1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30μmol d−1 g−1 and 0.02 and 0.28μmol d−1 g−1, respectively. Within the 120 d of anaerobic incubation only 6–17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61–100% CO2, 〈0.1–35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r=0.891) and total CH4 produced (r =0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992910
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  • 95
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    Herbivory pattern and induced responses to simulated herbivory inQuercus mongolica var.grosseserrata (1996)
    Springer
    Ecological research 11 (1996), S. 283-289 
    Details
    ISSN: 1440-1703
    Keywords: herbivory ; leaf life span ; leaf toughness ; nitrogen ; Quercus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal changes in leaf traits and the herbivory pattern ofQuercus mongolica var.grosseserrata were studied, and simulated herbivory experiments were carried out in order to evaluate leaf trait responses. Leaves ofQ. mongolica emerged simultaneously in spring and most were retained until autumn. Nitrogen concentration was highest when leaves first emerged and decreased rapidly with leaf age. Leaf mass per area (LMA) increased with leaf age. Herbivore attack was concentrated in the first 20 days after bud-break, which corresponded to the high nutritional value of the leaves for herbivores at this time. Simulated herbivory experiments indicated that LMA increased with artificial leaf damage, suggesting an increase in leaf toughness, and that nitrogen concentration decreased later in the season in comparison with intact leaves. As a result, herbivore attack following artificial leaf damage decreased with increasing initial leaf damage. However, leaf longevity was not affected by initial leaf damage. These responses were considered to be a strategy to disperse herbivory damage among leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02347785
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  • 96
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    Changes in nitrogen resources with increases in temperature during production of mushroom compost (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 379-384 
    Details
    ISSN: 1573-0972
    Keywords: Agaricus bisporus ; ammonia ; compost ; nitrogen ; thermophilic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The rise in temperature is an important event during the composting of lignocellulosic materials and has to be controlled and regulated to improve the biodegradation. Phase I mushroom composts were incubated under environmentally controlled conditions. When the temperature was pre-set at 65°C and then later at around 80°C, the microbial respiration and the biodegradations were hardly affected. However residual activities due to thermoresistant bacteria were still measured after 68 h at a constant temperature of 80°C. Significant changes in nitrogen resources were observed: loss of nitrogen from microbial products, an increase in the proportion of nitrogen in non-hydrolysable and stable forms, and an increase in volatilisation of ammonia. These changes were mainly due to physico-chemical mechanisms associated with disturbances in the structure of the microbial community.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340215
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  • 97
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    Estimation of the Importance of Spatially Variable Nitrogen Application and Soil Moisture Holding Capacity to Wheat Production (1999)
    Springer
    Precision agriculture 1 (1999), S. 27-38 
    Details
    ISSN: 1573-1618
    Keywords: CERES ; wheat ; soil moisture ; nitrogen ; variability ; precision agriculture ; spatial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Crop growth modelling techniques were used to investigate the performance of a wheat crop over a range of weather conditions, nitrogen application rates and soil types. The data were used to predict long term benefits of using spatially variable fertilizer application strategies where fertilizer application rate was matched to the soil type, against a strategy of uniform fertilizer application. The model was also run with modified soil properties to determine the importance of soil moisture holding capacity in the variability of crop yield. It was found that the benefits of spatially variable nitrogen management when fertilizer was applied at the beginning of the season were modest on average. The range of results for different weather conditions was much greater than the average benefit. A large proportion of the variability of crop performance between soil types could be explained by differing soil moisture holding capacity. Devising techniques for managing this variability was concluded to be important for precision farming of cereals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009973802295
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  • 98
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    A nitrogen and phosphorus herbage nutrient index as a tool for assessing the effect of N and P supply on the dry matter yield of permanent pastures (1996)
    Springer
    Nutrient cycling in agroecosystems 47 (1996), S. 59-69 
    Details
    ISSN: 1573-0867
    Keywords: fertilizer ; nitrogen ; nutrition ; pastures ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In order to propose consistent decision rules for fertilizer supply, a study was made on the effect of additions of N and P fertilizers and of their interaction on the above-ground dry matter yield of pastures during spring. The interaction between N and P could occur through nutrient acquisition or nutrient efficiency for growth. We therefore characterised the herbage N and P status (N and P index) from previously established critical curves of herbage mineral content according to above-ground dry matter. First we studied the effect of N and P addition on herbage nutrient status. Secondly, we expressed the above-ground dry matter as a function of the herbage nutrient status. This study consisted of four treatments applied to four permanent pastures which had a low phosphorus availability. The results showed a positive effect of P supply on the herbage nitrogen status, which may be due to an increase of organic matter mineralization or root growth. The P herbage status decreased only if N was supplied without P. The dry matter yield was positively related to the herbage nitrogen status, but a low P herbage status reduced the slope of the relationship. For the pastures studied, the indirect effect of P supply on above-ground dry matter, revealed by an increase in N index, was greater than its direct effect. This methodology allows us to distinguish the direct and indirect effects of N and P addition on herbage growth at field level. It could be used to propose consistent rules to manage jointly both N and P supplies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01985719
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  • 99
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    Nitrogen losses and fertilizer N use efficiency in irrigated porous soils (1996)
    Springer
    Nutrient cycling in agroecosystems 47 (1996), S. 197-212 
    Details
    ISSN: 1573-0867
    Keywords: ammonia volatilization ; coarse textured soils ; denitrification ; fertilizer N use efficiency ; irrigated soils ; leaching ; nitrification ; nitrogen ; porous soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Porous soils are characterized by high infiltration, low moisture retention and poor fertility due to limitation of organic matter and nitrogen (N). However, wherever irrigated and properly managed, these are among the most productive soils in the world. For sustained productivity and prevention of N related pollution problems, fertilizer N management in porous soils needs to be improved by reducing losses of N via different mechanisms. Losses of N through ammonia volatilization are not favoured in porous soils provided fertilizer N is applied before an irrigation or rainfall event. Ammonium N transported to depth along with percolating water cannot move back to soil surface where it is prone to be lost as NH3. Under upland conditions nitrification proceeds rapidly in porous soils. Due to high water percolation rates in porous soils, continuous flooding for rice production usually cannot be maintained and alternate flood and drained conditions are created. Nitrification proceeds rapidly during drained conditions and nitrates thus produced are subsequently reduced to N2 and N2O through denitrification upon reflooding. Indirect N-budget estimates show that up to 50% of the applied N may be lost via nitrification-denitrification in irrigated porous soils under wetland rice. High soil nitrate N levels and sufficient downward movement of rain water to move nitrate N below the rooting depth are often encountered in soils of humid and subhumid zones, to a lesser extent in soils of semiarid zone and quite infrequently, if at all in arid zone soils. The few investigations carried out with irrigated porous soils do not show substantial leaching losses of N beyond potential rooting zone even under wetland rice. However, inefficient management of irrigation water and fertilizer N particularly with shallow rooted crops may lead to pollution of groundwater due to nitrate leaching. At a number of locations, groundwater beneath irrigated porous soils is showing increased nitrate N concentrations. Efficient management of N for any cropping system in irrigated porous soils can be achieved by plugging losses of N via different mechanisms leading to both high crop production and minimal pollution of the environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01986275
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  • 100
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    Ammonia volatilization from urea as affected by the addition of iron pyrites and method of application (1996)
    Springer
    Nutrient cycling in agroecosystems 46 (1996), S. 97-101 
    Details
    ISSN: 1573-0867
    Keywords: ammonia loss ; iron pyrite ; nitrogen ; particle size ; placement ; surface-applied urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory incubations were conducted to determine the ammonia (NH3) loss from urea as affected by the addition of coarse and ground (fine) pyrites at 1:1, 1:2 and 1:5 urea: pyrite (w/w) ratios and methods of application (surfaceapplication, incorporation and placement). Coarse pyrites (〉-2mm) were not effective in reducing NH3 loss from urea when surface applied even at the highest ratio of pyrite (15.9% vs 18.7% without pyrite). Ground pyrites (0.1–0.25 mm), in 1:1 ratio, had about 5% less NH3 loss than the urea alone treatment. Higher ratios of pyrites reduced NH3 loss much more. Ammonia losses were the most with surface-applied urea (18.9%) and the least (13.5%) when placed (2.5 cm) below the soil surface. Addition of ground pyrite to surface-applied urea (1:1 ratio) decreased the loss to 13.2%. Urea+pyrite placed below the soil surface had the least loss (9.8%). Results indicate that combined application of urea and fine pyrite could reduce NH3 loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704309
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