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  • nitrogen  (49)
  • Mice
  • Models, Molecular
  • Springer  (52)
  • American Institute of Physics (AIP)
  • Nature Publishing Group (NPG)
  • 2010-2014
  • 1990-1994  (52)
  • 1990  (52)
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  • 2010-2014
  • 1990-1994  (52)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 4 (1990), S. 1-22 
    ISSN: 1573-0417
    Keywords: sulfate ; carbon ; nitrogen ; hydrogen ; organic matter ; enrichment factor ; lake sediments ; paleolimnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract This paper discusses the use of S as a paleolimnological tracer of limnetic sulfate concentration. A positive relationship (p〈0.05) was found between limnetic sulfate and sediment S concentrations for the Great Lakes, English Lakes, and lakes from the Adirondack and Northern New England regions. There is a positive correlation (p〈0.05) between C and S concentration in sediment across all regions studied. The importance of C in affecting S content in sediment was also examined by a series of cores taken at different water depths in Big Moose Lake (Adirondacks). There was a strong relationship between C and S among cores with sediment from deeper water having higher C and S concentrations (r 2=0.99). Sulfur from the shallower cores had greater concentrations of chromium-reducible S (pyrite), while cores from deeper waters had a greater proportion of organic S fractions including C-bonded S and ester sulfates. For assessing historical changes in S accumulation in sediments, enrichment factors were calculated for the PIRLA lakes. Pre-1900 net sediment accumulation rates of S were very similar across all regions. Sulfur enrichment was greatest in Adirondack sediment which had total post-1900 S accumulation of 1.1 to 7.4 times pre-1900 S accumulation. Sediment from Northern New England (NNE) generally had lower S concentration than Adirondack sediments and S enrichment factors ranged from 1.2 to 2.1. Sediment from the Northern Great Lakes States region had similar S concentration and distribution with depth to NNE sediment. In two Northern Florida lakes, sediment showed little variation in S concentration with depth, but in two other lakes from the same region, there was higher S concentration in deeper layers. Lakes which had the greatest enrichment factors also exhibited the most marked changes in C:S ratios. Ratios of C:N showed little variation (10.6 to 26.1) among the PIRLA lakes. A first order model indicated slow decomposition within these organic rich sediments. Elemental concentrations and ratios of sediment from a variety of lakes and reservoirs were complied. Maximum and minimum elemental ratios for all the data were 28 to 8.1 for C:N, 0.81 to 0.11 for C:H, and 675 to 12.5 for C:S, respectively. For the C:S ratios in all regions except the Great Lakes, the maximum ratio was less than 231. Both the maximum and minimum amount of N and H concentration of organic matter is related to biotic processes. The minimum concentration of S is regulated not only by nutrient demands but also by non-assimilatory processes. Sulfur incorporation into sediments is a function of a complex of factors, but limnetic sulfate concentration and organic matter content play a major role in regulating the S content of sediment. Further quantification of S incorporation pathways will aid in the paleolimnological interpretation of sediment S profiles. Such information is also important in assessing how S sediment pools will respond to decreases in limnetic sulfate concentration which may occur with decreases in inputs from acidic deposition.
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  • 2
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    Nutrient cycling in agroecosystems 21 (1990), S. 167-170 
    ISSN: 1573-0867
    Keywords: Mo ; interaction ; soybean ; deficiency ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Recent on-farm liming experiments showed that Mo deficiency in soybean [Glycine max (L.) Merr.] is widespread in northern Alabama. In contrast, a long-term, fertility-rotation experiment in the same area showed no response to Mo during 33 yr when Mo was added bienially to corn [Zea mays L.] in the rotation; however, soybean foliage had the chlorotic appearance of Mo deficiency. The objective of this study was to determine if Mo deficiency was being missed by comparing only two fertilizer treatments. Each rotation-fertilizer treatment plot was split into two, with one-half receiving MO at a 100 g ha−1 foliar rate after seedling emergence, while the other half received none. Yields were increased by Mo in 13 to 16 fertilizer treatments in 1985 and 15 out of 16 in 1986. Leaf-N concentrations and seed weight had comparable increased amounts by the Mo supplement. Without the Mo supplement, there was a response to lime but not to P, K, or a Mo-containing micronutrient mixture; with the Mo supplement, there was no response to liming, but a definite response to P and K (in addition to Mo). The lack of response to Mo when applied to corn in a 2-yr rotation over 33 yr led to the erroneous conclusion that these soils were not Mo deficient for soybean.
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  • 3
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    Nutrient cycling in agroecosystems 22 (1990), S. 71-78 
    ISSN: 1573-0867
    Keywords: Boron ; critical level ; grain ; nitrogen ; nodulation ; nutrition ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A two year field study on the effect of nitrogen N and boron B fertilization on the nodulation, mineral nutrition and grain yield of cowpea was carried out in the Nigerian savanna where fairly widespread B deficiency has been reported. Treatments consisted of four levels of N (0, 15, 30 and 60 kg/ha in 1986 and 0, 15, 30 and 45 kg/ha in 1987) and three levels of B (0, 1.5 and 3.0 kg/ha). Cowpea responded positively though nonsignificantly to N fertilization up to 30 kg N/ha. However, N had no effect on the N, P, K and B content of index leaves. Boron application consistently reduced grain yield. Like N, applied B had no effect on the N, P, K concentration of index leaves but increased B concentration highly significantly (P 〈 0.001). The critical level of B toxicity in index leaves was approximated to be 21pm under field condition. Application of N and B depressed nodulation.
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  • 4
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    Nutrient cycling in agroecosystems 23 (1990), S. 97-103 
    ISSN: 1573-0867
    Keywords: Carbon ; mineralization ; nitrogen ; organic fertilizer ; temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The C and N mineralization characteristics of two organic N fertilizers were determined in a soil-less incubation system at three temperature regimes. Protox (derived from activated sewage sludge) initially degraded more rapidly by microbial action compared with dried blood. However, dried blood released more CO2-C and inorganic N towards the end of the incubation periods. The rate of microbial degradation increased with temperature. Mineralization characteristics of protein-based N sources are discussed in relation to organic N nutrition of vegetable crops.
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  • 5
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    Nutrient cycling in agroecosystems 23 (1990), S. 105-112 
    ISSN: 1573-0867
    Keywords: Ammonium ; fertigation ; nitrate ; nitrogen ; trickle irrigation ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The movement and transformations of ammonium-, urea- and nitrate-N in the wetted volume of soil below the trickle emitter was studied in a field experiment following the fertigation of N as ammonium sulphate, urea and calcium nitrate. Effects on soil pH in the wetted volume were also investigated. During a fertigation cycle (emitter rate 2lh−1) applied ammonium was concentrated in the surface 10 cm of soil immediately below the emitter and little lateral movement occurred. In contrast, because of their greater mobility in the soil, fertigated urea and nitrate were more evenly distributed down the soil profile below the emitter and had moved laterally in the profile to 15 cm radius from the emitter. The conversion of applied N to nitrate-N was more rapid when urea rather than ammonium-N was applied suggesting that the accumulation of large amounts of ammonium below the emitter in the ammonium sulphate treatment probably retarded nitrification. Following their conversion to nitrate-N, both fertigated ammonium sulphate and urea caused acidification in the wetted soil volume. Acidification was confined to the surface 20 cm of soil in the ammonium sulphate treatment, however because of its greater mobility, fertigation with urea (2lh−1) resulted in acidification occurring down to a depth of 40 cm. Such subsoil acidity is likely to be very difficult to ameliorate. Increasing the trickle discharge rate from 2lh−1 to 4lh−1 reduced the downward movement of urea and encouraged its lateral spread in the surface soil. As a consequence, acidification was confined to the surface (0–20 cm) soil.
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  • 6
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    Theoretical and applied genetics 79 (1990), S. 131-136 
    ISSN: 1432-2242
    Keywords: Selection response ; Metabolic rate ; Inheritance of activity ; Mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The aim of this study was to examine the differences in physical activity and their contribution to differences in energy utilization in mice, selected either high or low for food intake, adjusted for body weight, which show correlated responses in lean content and metabolic rate. Simultaneous measurements of fasting metabolic rate and activity were made in lines of mice selected at either: a young age, 4-to 6-week food intake corrected for 4-week body weight; or an older age, 8- to 10-week food intake corrected for mean weight at 8 and 10 weeks of age. Correlated response in metabolic rate was found to have been accompanied by changes in locomotor activity near the ages at selection in both sets of lines. Activity, however, accounted for only a small proportion of variation in fasting heat production, generally less than 5%, although a highly positive correlation (r=0.63) between the two traits was found. It was concluded that selection for food intake adjusted for body weight has led to correlated response in physical activity. In consequence, mice selected in the upward direction expend some of the excess energy intake rather than assimilating it as body mass and are, therefore, slightly leaner than their counterparts selected in the downward direction.
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  • 7
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    Theoretical and applied genetics 80 (1990), S. 625-630 
    ISSN: 1432-2242
    Keywords: Selection ; Mice ; Litter size ; Litter weight ; Reproductive performance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Five 60-pair lines of mice were selected for seven generations for the following criteria: number born alive (LSO), random selection of litters (LC), number born alive divided by the weight of the dam at 9 weeks (LSO/DWT), total litter weight weaned divided by the weight of the dam at 9 weeks (LWT/DWT), and weight of litter weaned (LWT). All traits were measured in the first parity only and litters were not standardized. Realized heritabilities for LSO, LWT, LSO/DWT, and LWT/ DWT were 0.10± 0.06, 0.11±0.07, 0.22 ± 0.04, and 0.22 ± 0.08, respectively. Selection response for the two ratio lines was due to correlated responses in the respective numerators, LSO and LWT, as DWT did not decrease. In terms of improving LWT, selection for LWT/ DWT was three times as effective as selection for LSO/ DWT.
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  • 8
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    Theoretical and applied genetics 79 (1990), S. 268-272 
    ISSN: 1432-2242
    Keywords: Mice ; Lifetime ; Performance ; Longevity ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An experiment was conducted in mice to examine whether selection can increase reproductive life and lifetime production of progeny. Mice in two lines with litter size standardized at birth and in two lines without standardization were pair-mated at 7 weeks of age and maintained as long as they produced litters up to 382 days. Progeny from the sixth litters were used to maintain the four selected lines, while progeny from the first litters were bred to maintain unselected control lines. Selected and control lines were compared at five and six generations of the selected lines. Contemporary comparisons revealed that the length of reproductive life and most lifetime production traits were significantly greater in the selected than in control lines. Realized heritability of the length of reproductive life ranged from 0.08 to 0.13. It was concluded that the length of reproductive life and lifetime production in mice can be increased by selection.
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  • 9
    ISSN: 1573-5036
    Keywords: disturbance ; fertilizer ; nitrogen ; nutrient enrichment ; phosphorus ; secondary succession ; species richness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of annual additions of mineral N and P (100 kg ha−1) on plant species composition and annual aboveground net primary production (ANPP) were investigated during the first three years following disturbance in a semi-arid ecosystem. Additions of N reduced richness of perennial plant species during years 2 and 3, while P reduced the number of perennial species only in year 3. From year 1 to year 2, annual and biennial species richness declined in all treatments while ANPP of annual species increased greatly. Added N increased ANPP of annual species while it decreased ANPP of most perennial species relative to the unfertilized control treatment. Community similarities were higher for the control and native vegetation than for other pairs of treatments using both species presence and plant production data. Nitrogen additions have retarded but not completely arrested secondary succession in this system.
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  • 10
    ISSN: 1573-5036
    Keywords: eucalypt ; foliar analysis ; legume ; nitrogen ; phosphorus ; plant nutrients ; plant analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The sensitivity of tissue nutrient concentrations to changes in plant age and the supply of P and N was compared between leaves and associated twigs in two forest species. In a young regrowth stand, tissues were sampled on three occasions from the mid-crown position of karri (Eucalyptus diversicolor F. Muell.) and Bossiaea laidlawiana Tovey and Morris, a major understorey legume. Leaves and twigs were also sampled from young plants of B. laidlawiana growing in a mature eucalypt stand to which P treatments had been applied. Nitrogen application increased N concentrations in twigs of karri and B. laidlawiana, but not in leaves. Phosphorus application increased P concentrations in both leaves and twigs of karri but the average increases were proportionally greater in twigs (65%) than in leaves (36%). Over the sampling period, P concentrations in leaves declined, while those in twigs were relatively stable. In B. laidlawiana, P supply also had a larger effect on P concentrations in twigs than in leaves. Addition of 200 kg P ha−1 increased average P concentrations in twigs by 109% in the regrowth stand and by 215% in the mature stand while the corresponding increases in leaves were only 11% and 27%. Concentrations of other nutrients in both species were also affected by N and P application, the most notable being a decline in the concentrations of the minor nutrients, Zn and Cu, with increased P supply. The increased N concentrations in twigs of karri, and the increased P concentrations in tissues of both species, were associated with responses of karri to added N and P, and of B. laidlawiana to added P. This indicates that tissue concentrations of N and P were generally below critical concentrations where N and P were not applied. The results show that for these species twigs may be a better tissue than leaves for diagnosing deficiencies or predicting N and P requirements. The ratio of P concentrations in twigs to P concentrations in leaves also increased with added P. It is suggested that this ratio may be a useful index if it reduces the variability caused by sampling position within the crown or genetic differences between plants.
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  • 11
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    Plant and soil 123 (1990), S. 67-71 
    ISSN: 1573-5036
    Keywords: Dalbergia sissoo ; fertilization ; nitrification ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The influence of added ammonium, phosphorus, potassium, and gypsum on net nitrogen mineralization was studied in soil beneath a six-year-old plantation of the N2-fixing tree Dalbergia sissoo in Pakistan. Soil with and without amendments was placed in polyethylene bags and incubated, buried in the soil, for 30 days. After that time the soil was analyzed and net ammonium and nitrate production and net nitrogen mineralization were calculated. The addition of ammonium stimulated nitrification indicating that the process was substrate limited. The inhibition of nitrification by Nitrapyrin showed that the process is autotrophic in these soils. Gypsum addition lowered soil pH from 8.0 to 7.2 and significantly stimulated ammonification, nitrification and net nitrogen mineralization. The addition of potassium more than tripled the soil K:Na ratio. Net ammonium and nitrate production and net nitrogen mineralization all increased in this treatment. The addition of phosphorus had no significant effect on soil nitrogen dynamics.
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  • 12
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    Plant and soil 127 (1990), S. 213-218 
    ISSN: 1573-5036
    Keywords: dry matter yield ; nickel ; nitrogen ; nutrient concentration ; wheat roots ; wheat tops
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A glasshouse experiment was conducted to study the effect of Ni on the growth and nutrients concentration in wheat (Triticum aestivum Cv. WH 291) in the presence and absence of applied N as urea. Responses to N application were observed up to 120 μg N g−1 soil. No response to Ni was observed in the dry matter yield of wheat tops (leaves + stem) in the absence of applied N while in the presence of applied N, significant yield increases were obtained at 12.5μg Ni g−1 soil. Nickel was not toxic to wheat up to 50μg Ni g−1 soil in the presence of 120μg N g−1 soil. Nitrogen and Ni concentration in wheat tops and roots increased with increasing levels of applied N and Ni, respectively. Applied Ni had an antagonistic effect on N concentration. Similarly, N reduced the Ni concentration in the wheat tissues. Positive growth responses to Ni were associated with 22 and 15μg Ni g−1 in wheat tops, in the presence of applied N at 60 and 120μg N g−1 soil, while Ni toxicity was associated with 63, 92.5 and 112.5μg Ni g−1 in wheat tops, in the absence and presence of applied N at 60 and 120μg N g−1 soil, respectively.
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  • 13
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    Plant and soil 128 (1990), S. 21-30 
    ISSN: 1573-5036
    Keywords: allocation ; clearcut ; mineralization ; nitrogen ; prescribed fire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Past and current work on biological processes related to nitrogen fluxes and cycling in natural and disturbed Mediterranean forest sites are discussed. In natural conditions, the main point reviewed is mineral nitrogen availability in the soil, and particularly the process of mineralization (ammonification, nitrification) in the field as well as nitrogen uptake by Pinus pinea. Some aspects of nitrogen translocation within the trees are also considered. Perturbation of the nitrogen status, and especially nitrogen mineralization, as a result of manipulation of forest sites are discussed by comparing both a holm oak coppice with a clearcut and a Pinus halepensis woodland before and after prescribed fire.
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  • 14
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    Plant and soil 125 (1990), S. 19-27 
    ISSN: 1573-5036
    Keywords: amino acid ; deficiency ; essentiality ; malate ; micronutrient ; nickel ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Barley (Hordeum vulgare L. cv. ‘Onda’) plants were grown in nutrient solutions supplied either 0 (no Ni added), 0.6, or 1.0 μM NiSO4. Plants supplied 0 μM Ni developed Ni deficiency symptoms; Ni deficiency resulted in the disruption of nitrogen metabolism, and affected the concentration of malate and various inorganic anions in roots, shoots, and grain of barley. The concentrations of 10 of the 11 soluble amino acids determined were 50–200% higher in 30-day-old shoots of plants supplied inadequate Ni levels than in shoots of Ni-supplied plants. The total concentration of all amino acids determined was higher in roots and grain of Ni-deficient plants. Concentrations of NO3 - and Cl- were also higher in Ni-deficient barley shoots than in Ni-sufficient barley shoots. In contrast, the concentration of alanine in shoots of Ni-deficient barley was reduced to one-third of the concentration in Ni-sufficient plants. The shoot concentrations of malate and SO4 2- were also depressed under Ni-deficient conditions. Total nitrogen concentration in grain, but not in shoots, of Ni-deficient plants was significantly increased over that found in Ni-adequate plants. Nickel deficiency results in marked disruptions of N metabolism, malate and amino acid concentrations in barley. These results are discussed in view of the possible roles of Ni in plants.
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  • 15
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    Plant and soil 125 (1990), S. 119-128 
    ISSN: 1573-5036
    Keywords: ammonia ; application method ; application rate ; environment ; grassland ; nitrogen ; slurry ; volatilization ; wind speed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three experiments were conducted to examine the influence of slurry application rate, wind speed and applying slurry in narrow bands on ammonia (NH3) volatilization from cattle slurry surface-applied to grassland. The experiments were conducted in the field using a system of small wind tunnels to measure NH3 loss. There was an inverse relationship between slurry application rate and the proportion of NH4 +-N volatilized. From slurry applied at 20, 40, 60, 80, 100 and 120 m3 ha-1, the respective proportions of NH4 +-N lost by NH3 volatization in 6 days were 60, 56, 49, 40, 44 and 44%. The negative relationship was most pronounced in the first 24 hours after application when 57–77% of the total loss for 6 days occurred. Wind speed had a positive effect on NH3 volatilization, although the effect was small in relation to the total loss; increasing the wind speed from 0.5 to 3.0 m s-1 increased the total 5 day loss by a factor of 0.29. The effect of wind speed was also most pronounced in the first 24 hours when much of the NH3 loss took place. The effect of reducing the surface area of the applied slurry was examined by comparing NH3 volatilization from slurry broadcast across plots with that applied in narrow bands. Although the rate of NH3 volatilization was considerably smaller from the banded application immediately after the slurry was applied, the difference between the treatments progressively narrowed until 2 days after application, after which a higher rate was maintained from the banded slurry. After 5 days the total loss from the banded application was 83% of that from broadcast slurry.
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  • 16
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    Plant and soil 125 (1990), S. 109-117 
    ISSN: 1573-5036
    Keywords: ammonia ; environment ; grassland ; mechanical separation ; nitrogen ; slurry ; volatilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three experiments were conducted using a system of small wind tunnels to measure ammonia (NH3) volatilization from cattle slurry after surface application to land. In each experiment slurry was applied at a rate equivalent to 80 m3 ha-1, providing the equivalent of approximately 100 kg NH4 +-N ha-1. The first experiment compared NH3 volatilization from the liquid fraction obtained by mechanical separation of slurry with that from unseparated slurry. The total NH3 loss over six days from unseparated and separated slurry were very similar, being 38 and 35% respectively of the NH4 +-N applied. For the first five hours, the rate of NH3 loss was higher from the unseparated slurry, thereafter it was consistently lower. In the second experiment, slurry was ponded in a tray to examine whether impeded infiltration or changes in the NH4 + concentration or overall pH of the slurry influenced the rapid decline in rate soon after application that is characteristic of NH3 volatilization from animal slurries applied to land. It appeared, however, that other factors such as resistance to diffusion within the slurry and/or at the slurry surface were mostly responsible for the rapid decline in rate. In the third experiment, in which NH3 volatilization was measured from slurry applied to grassland or bare soil, the total loss from slurry applied to grassland was approximately 1.5 times that from slurry applied to bare soil.
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  • 17
    ISSN: 1573-5036
    Keywords: calcium ; copper ; desert ; ground water ; iron ; magnesium ; manganese ; nitrogen ; phosphorus ; Prosopis glandulosa ; rooting patterns ; sodium ; symbiotic nitrogen fixation ; trace metals ; water table ; water use efficiency ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Mesquite plants (Prosopis glandulosa var. Torreyana) were grown in 2-m long columns 20 cm in diameter, and provided with a constant, stable ground water source 10 cm above the sealed base of the column. Ground water contained 0, 1 or 5 mM nitrate, or a mixed salt solution (1.4, 2.8, or 5.6 dS m-1) with the ionic ratios of ground water found in a field stand of Prosopis at Harper's Well (2.8 dS m-1). Water uptake in the highly salinized columns began to decrease relative to low salt columns when soil salinity probes 30 cm above the column base read approximately 28 dS m-1, a potential threshold for mesquite salt tolerance. Prosopis growth increased with increasing nitrate, and decreased with increasing salinity. Water use efficiency was little affected by treatment, averaging approximately 2 g dry matter L-1 water used. Most fine roots were recovered from a zone about 25 cm above the ground water surface where water content and aeration appeared to be optimal for root growth. Root-shoot ratio was little affected by nitrate, but increased slightly with increasing salinity. Plant tissue P concentrations tended to increase with increasing salinity and decrease with increasing N, approaching potentially deficient foliage concentrations at 5 mM nitrate. The whole-plant leaf samples increased in sodium concentration both with added salt and with added nitrate. Foliar manganese concentrations increased with increasing salt in the absence of nitrate. Concentrations of sodium in leaves were low (〈10 g kg-1), considering the high salt concentrations in the ground water. Prosopis appears to exclude sodium very effectively, especially from its younger leaves. Although Prosopis is highly salt tolerant, the degree to which it utilizes soil nitrate in place of biologically fixed N may lower its salinity tolerance and affect its nutrient relations in phreatic environments.
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  • 18
    ISSN: 1573-5036
    Keywords: grassland ; leaching ; leaf litter ; macro-organic matter ; mineralization ; nitrogen ; ploughing ; roots ; stubble
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The amounts of organic matter in the stubble, litter, root and soil macro-organic matter fractions of two swards of perennial ryegrass that had received normal applications of either fertilizer or cattle urine were, on average for the four fractions, about 3000, 500, 11,500 and 8,800 kg ha−1. The swards had been established 8 or 15 years previously and each was sampled at intervals over a period of about one year. The amounts of N contained in the four fractions were, on average, 68, 12, 249 and 240 kg ha−1, a total of 569 kg N ha−1. With other swards, increasing rates of application of fertilizer N were found to have little effect on the amounts of organic matter in stubble and roots. Concentrations of N in the organic matter of the stubble and roots, however, increased significantly with increasing rate of fertilizer application, though, with stubble, moderate rates of application had little effect. Assessments based on these data, together with other published information, indicate that the amount of N mineralized from the combined stubble, litter, root and macro-organic matter fractions during the first year after ploughing may range from about 40 kg to at least 360 kg N ha−1 depending on the age of the sward and its recent management. The amount mineralized is likely to increase with age of sward, with increasing rate of fertilizer N and with utilisation by grazing rather than cutting.
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  • 19
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    Plant and soil 123 (1990), S. 155-159 
    ISSN: 1573-5036
    Keywords: cultivars ; nitrogen ; roots ; tropic climate ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Due to the high price of fertilizer the input of N for grain maize production must be kept low in many parts of the world. Low input cultivars have been suggested to meet this requirement. Screening of a group of tropical cultivars revealed two high input, two low input and two intermediate cultivars with regard to N utilization. One of the causes of an interaction between genotype and N fertilization might be differences in root morphology. Screening for such differences at an early seedling stage would facilitate the selection for low input varieties. This hypothesis was tested by growing seedlings of the six varieties at different levels of N until the fourth leaf stage. There was no significant interaction between genotypes and N supply. At low and medium N supply, the total seedling biomass was the same but at low N a higher proportion of dry weight was found in the roots. Total biomass was reduced at high N. Low input and intermediate cultivars had higher shoot and root dry weights than did high input cultivars but no significant differences in root surface area were found. Root surface area was greatest at low N. Number and total length of seminal roots were significantly lower for high input varieties which, in combination with a relatively high root surface area, points to an intensive root type.
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  • 20
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    Plant and soil 124 (1990), S. 33-37 
    ISSN: 1573-5036
    Keywords: leaf area ; nitrogen ; mineral nutrition ; phosphorus ; photoperiod ; Triticum ; wheat ; spikelet initiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of N and P on the number of spikelets of spring wheat (Triticum aestivum L.), grown in nutrient solution, were studied under 8 h and 16 h photoperiods. The effect of P was apparent only at a high rate of N supply and the effects of N were increased significantly at a high rate of P supply. Increasing N supply increased the number of spikelets due to a promotion of the rate of spikelet initiation. It also increased the leaf-blade area and the dry matter weight of the plants at the stage of terminal spikelet initiation. These effects of N were much greater under the short photoperiod than under the long photoperiod. The practical significance of these findings for winter-grown wheat in temperate regions is pointed out.
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  • 21
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    Plant and soil 128 (1990), S. 97-101 
    ISSN: 1573-5036
    Keywords: calcium ; magnesium ; nitrogen ; nitrogen saturation ; Norway spruce ; nutritional imbalance ; Picea abies ; soil solution ; sulphur/nitrogen ratio ; tree nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Differences in nitrogen cycling and in the nutrition of trees are significantly coupled to the levels of nitrogen input and to the nitrate levels in the soil solution. Relatively high nitrogen supply can cause unbalanced nutrition on sites which contain either low or moderate amounts of other nutrients. This is indicated by low cation/nitrogen ratios in foliage and also by the S/N ratio falling temporarily below 0.030.
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  • 22
    ISSN: 1573-5117
    Keywords: phytoplankton collapses ; hypertrophic ; nitrogen ; phosphorus ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Short-term changes in phytoplankton and zooplankton biomass have occurred 1–3 times every summer for the past 5 years in the shallow and hypertrophic Lake Søbygård, Denmark. These changes markedly affected lake water characteristics as well as the sediment/water interaction. Thus during a collapse of the phytoplankton biomass in 1985, lasting for about 2 weeks, the lake water became almost anoxic, followed by rapid increase in nitrogen and phosphorus at rates of 100–400 mg N M−2 day−1 and 100–200 mg P m−1 day−1. Average external loading during this period was about 350 mg N m−2 day−1 and 5 mg P m−2 day−1, respectively. Due to high phytoplankton biomass and subsequently a high sedimentation and recycling of nutrients, gross release rates of phosphorus and nitrogen were several times higher than net release rates. The net summer sediment release of phosphorus was usually about 40 mg P m−2 day−1, corresponding to a 2–3 fold increase in the net phosphorus release during the collapse. The nitrogen and phosphorus increase during the collapse is considered to be due primarily to a decreased sedimentation because of low algal biomass. The nutrient interactions between sediment and lake water during phytoplankton collapse, therefore, were changed from being dominated by both a large input and a large sedimentation of nutrients to a dominance of only a large input. Nitrogen was derived from both the inlet and sediment, whereas phosphorus was preferentially derived from the sediment. Different temperature levels may be a main reason for the different release rates from year to year.
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  • 23
    ISSN: 1573-5117
    Keywords: submerged macrophyte ; Ceratophyllum demersum ; litter ; decomposition ; pyrolysis mass spectra ; residual mass ; carbon ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was made of decomposition ofCeratophyllum demersum litter over a 17-day period under controlled conditions of temperature and oxygen (5, 10 and 18 °C; aerobic and anaerobic) and over a 169-day period in the field (Lake Vechten, The Netherlands). Litter, water and sediment were sampled on the 0, 2, 4, 7 and 17th day under controlled conditions and on the 0, 17, 49, 127 and 169th day in the field. The litter was analyzed quantitatively for dry mass, ash, carbon, nitrogen, phosphorus and qualitatively of organic composition by pyrolysis mass spectrometry. The water was analyzed for the elemental concentrations of organic carbon (total and dissolved), nitrogen (total, ammonia and particulate) and phosphorus (total and orthophosphate) and for the concentrations of photosynthetic pigments and bacteria. The sediment was analyzed for the elemental concentrations of nitrogen, carbon and phosphorus, and for bacterial numbers. The pattern of litter mass loss fitted an exponential model fairly well. Mass decreased faster under controlled aerobic than under anaerobic conditions and the decrease was stimulated by increasing temperature, relatively more in the range of 5 to 10 °C (by 20%) than in the range of 10 of 18 °C (by 2%). The residual mass ranged from 73 to 43% of initial under controlled aerobic conditions and from 84 to 65% under anaerobic conditions after 17 days. It decreased far less in the field, to 38% of initial mass in the field after 169 days. The litter initially lost a carbohydrate fraction by leaching in all treatments. The protein content decreased initially as well but increased subsequently at increasing temperature stimulated under anaerobic conditions. The changes in organic composition were correlated with those in nitrogen but not with those in carbon and phosphorus contents. The organic composition of litter incubated in the field differed from that of litter incubated in the laboratory. The field residues contained less proteinaceous material than the laboratory residues. The changes in carbon, nitrogen and phosphorus concentrations in the litter showed different patterns. The carbon concentration generally increased, the nitrogen concentration initially dropped and increased subsequently, and the phosphorus concentration initially dropped and remained relatively constant subsequently. Chemical immobilization of the decomposition process may have occurred in the laboratory, but was unlikely in the field. Carbon, nitrogen and phosphorus left the litter initially largely in particulate form and were recovered in the water. The ratio dissolved: total nutrient concentration was lower under controlled aerobic than under anaerobic conditions. Increasing temperature stimulated bacterial use of dissolved organic carbon and nitrogen. A rapid nutrient flow occurred from macrophyte litter, via water to sediment. The phytoplankton biomass in the water was greatly stimulated by substances freed from the decomposing litter. Diatoms increased generally relatively more than green algae, predominating alternatively with green algae under aerobic conditions and continuously under anaerobic conditions. Bacterial numbers in the water initially increased, partly due to transgression of bacteria from the sediment-water interface to the water and partly due to an actual increase in community biomass. The bacteria returned largely to the sediment-water interface, stimulated by increasing temperature, as most of the substrate readily usable by them had left the litter in the litter-bag and was associated with the upper sediment layers. It is feasible that the annual die-off of theC. demersum population of Lake Vechten barely affects nutrient cycling in the lake, because the contribution to the nutrient pools of the lake when fully mixed is only small. However, small particles originating from decomposingC. demersum litter may influence the lake considerably by decreasing water transparency and serving as a food source for filter-feeders and detritivorous macrofauna.
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    Hydrobiologia 202 (1990), S. 61-69 
    ISSN: 1573-5117
    Keywords: Gulls ; phosphorus ; nitrogen ; eutrophication ; excretion ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nutrient excretion rates and the annual contribution of P from the feces of the gullsLarus argentatus andL. marinus (and of N fromL. argentatus) to the nutrient budget of Gull Pond (Wellfleet), a soft water seepage lake, have been estimated. Intensive year-round gull counts by species were combined with determinations of defecation rate and the nutrient content of feces to quantitatively assess the P loading rates associated with regular gull use of this coastal pond on a seasonal and annual basis. Total P loading from gulls was estimated to be 52 kg yr−1, with 17 kg fromL. argentatus and 35 kg fromL. marinus, resulting from about 5.0 × 106 h yr−1 and 1.7 × 106 h yr−1 of pond use. This compares with P loading estimates of 67 kg yr−1 from upgradient septic systems, 2 kg yr−1 from precipitation and 3 kg yr−1 from unpolluted ground water. Fifty-six percent of annual gull P loading was associated with migratory activity in late fall. Estimated annual N loading byL. argentatus was 14 kg TKN, 206 g NO3-N, and 1.85 g g NH3-N.
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  • 25
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; bluegill ; plankton ; mesocosm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We conducted an outdoor mesocosm experiment of factorial design consisting of three levels of nutrient supply (no nutrient addition and additions of nitrogen and phosphorus in ratios of 10:1 and 45:1) cross-classified with two levels of bluegill (Lepomis macrochirus) (presence and absence). Nutrient supply significantly affected total phosphorus (TP), total nitrogen (TN), TN: TP ratio, turbidity, Secchi depth, phytoplankton chlorophyll, filamentous blue-green algae, periphyton chlorophyll, Asplanchna and non-predatory rotifers. The presence of bluegill significantly increased TP, turbidity, diatoms, unicellular green algae, colonial blue-green algae, filamentous blue-green algae, periphyton chlorophyll, Asplanchna and non-predatory rotifers, and decreased Secchi depth, cladocerans, cyclopoid copepodids, copepod nauplii and chironomid tube densities. Nutrient supply and fish effects were not independent of each other as shown by significant nutrient × fish interaction effects for TP, Secchi depth, filamentous blue-green algae, periphyton chlorophyll, Asplanchna and non-predatory rotifers.
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  • 26
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    Hydrobiologia 202 (1990), S. 61-69 
    ISSN: 1573-5117
    Keywords: Gulls ; phosphorus ; nitrogen ; eutrophication ; excretion ; nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nutrient excretion rates and the annual contribution of P from the feces of the gulls Larus argentatus and L. marinus (and of N from L. argentatus) to the nutrient budget of Gull Pond (Wellfleet), a soft water seepage lake, have been estimated. Intensive year-round gull counts by species were combined with determinations of defecation rate and the nutrient content of feces to quantitatively assess the P loading rates associated with regular gull use of this coastal pond on a seasonal and annual basis. Total P loading from gulls was estimated to be 52 kg yr−1, with 17 kg from L. argentatus and 35 kg from L. marinus, resulting from about 5.0 × 106 h yr−1 and 1.7 × 106 h yr−1 of pond use. This compares with P loading estimates of 67 kg yr−1 from upgradient septic systems, 2 kg yr−1 from precipitation and 3 kg yr−1 from unpolluted ground water. Fifty-six percent of annual gull P loading was associated with migratory activity in late fall. Estimated annual N loading by L. argentatus was 14 kg TKN, 206 g NO3-N, and 1.85 g g NH3-N.
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    Hydrobiologia 203 (1990), S. 93-97 
    ISSN: 1573-5117
    Keywords: sediments ; nitrogen ; phosphorus ; nutrient limitation ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A diffusion enrichment technique is presented which allows for chemical enrichment of soft surficial and shallow subsurface sediments and subsequent measurement of O2 production. The sediment is enriched by inserting a perforated tube containing dialysis tubing filled with a nutrient/agar mixture. O2 production by surficial sediment is measured using an inverted, translucent, polyethylene chamber over the sediment. The inside of the chamber contains a collapsible bag connected to the water outside the chamber. When water overlying the sediment is withdrawn from a sampling port, it is displaced with water from outside the chamber, thus preventing contamination of water samples with pore water from below. The technique was tested by enriching near-shore sediments in a large oligotrophic lake with inorganic N and P. NHinf4/p+ additions significantly stimulated benthic primary production as measured by 02 production, whereas enrichment with POinf4/3- had no effect.
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  • 28
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphate ; phytoplankton ; Mediterranean lagoon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A network of 63 stations was used on four occasions (June 1986, October 1986, February 1987, and May 1987) to study the spatio-temporal distribution of inorganic nutrients in Thau Lagoon (‘l'étang de Thau’), which covers 7500 hectares on the French Mediterranean coast. Three environmental factors, revealed by multiple regression models, govern the distributions observed. Allochthonous inputs from the watershed enrich the environment with nitrogen and phosphorus compounds in the winter and autumn. Internal sources are essentially localized in the shellfish breeding zone of the lagoon. In the summer, shellfish excretions and the rapid remineralization of organic deposits produce ammonium ions. Uptake by phytoplankton has a much larger impact on the seasonal variation of inorganic nitrogen than on that of phosphorus; the latter is present in excess in the lagoon waters. Thus, nitrogen appears to be the primary limiting nutrient for the development of the chorophyllous biomass.
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    Biogeochemistry 10 (1990), S. 67-79 
    ISSN: 1573-515X
    Keywords: deserts ; ecosystem ; nitrogen ; nutrient cycling ; soils ; southwestern United States
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A lower limit for nitrogen loss from desert ecosystems in the southwestern United States was estimated by comparing nitrogen inputs to the amount of nitrogen stored in desert soils and vegetation. Atmospheric input of nitrogen for the last 10 000 years was conservatively estimated to be 2.99 kg N/m2. The amount of nitrogen stored in desert soils was calculated to be 0.604 kg N/m3 using extant data from 212 profiles located in Arizona, California, Nevada, and Utah. The average amount of nitrogen stored in desert vegetation is approximately 0.036 kg N/m2. Desert conditions have existed in the southwestern United States throughout the last 10 000 years. Under such conditions, vertical leaching of nitrogen below a depth of 1 m is small (ca. 0.028 kg N/m2 over 10 000 years) and streamflow losses of nitrogen from the desert landscape are negligible. Thus, the discrepancy found between nitrogen input and storage represents the amount of nitrogen lost to the atmosphere during the last 10 000 years. Loss of nitrogen to the atmosphere was calculated to be 2.32 kg N/m2, which is 77% of the atmospheric inputs. Processes resulting in nitrogen loss to the atmosphere from desert ecosystems include wind erosion, ammonia volatilization, nitrification, and denitrification. Our analysis cannot assess the relative importance of these processes, but each is worthy of future research efforts.
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    Biogeochemistry 11 (1990), S. 1-22 
    ISSN: 1573-515X
    Keywords: disturbance ; ecosystems ; forests ; indirect interactions ; landscape ecology ; Minnesota ; nitrogen ; nutrient cycling ; path analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Path analysis was used to determine the importance of long-term disturbance regime and the relative importances of correlations among vegetation patterns, disturbance history, and nitrogen (N) mineralization in old-growth forests of northwestern Minnesota. Leaf biomass (estimated by allometric equations), fire history (from fire scars on Pinus resinosa trees), and N mineralization rates (estimated from incubationsin situ) were determined from sample plots dominated by Betula papyrifera, Populus tremuloides, andP. grandidentata a mixture ofAcer saccharumandTilia americana, or Quercus borealis andOstrya virginiana. Results showed that topographic and soil-moisture controls on N mineralization, vegetation patterns, and disturbance are substantially stronger than is suggested by direct correlation. Indirect interactions among ecosystem variables played in important role. These interactions probably include the tendency for species that cycle large amounts of N to colonize more mesic sites that burned rarely in the past. Soil moisture was correlated both directly with N mineralization and indirectly, through its effects on vegetation pattern, and thus, litter quality. Although disturbance regime also depended on topography, the strengths of relationships between disturbance regime and other variables were relatively weak. These dependencies suggested that long-term fire regime is probably more a consequence than a cause for vegetation and fertility patterns. Topography, through its effects on soil moisture and microclimate, is an overriding influence on ecosystem properties, which in turn influence fire regime.
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  • 31
    ISSN: 1573-515X
    Keywords: cumulative ; flow ; GIS ; landscape ; lead ; nitrogen ; phosphorus ; suspended solids ; watershed ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A method was developed to evaluate the cumulative effect of wetland mosaics in the landscape on stream water quality and quantity in the nine-county region surrounding Minneapolis—St. Paul, Minnesota. A Geographic Information System (GIS) was used to record and measure 33 watershed variables derived from historical aerial photos. These watershed variables were then reduced to eight principal components which explained 86% of the variance. Relationships between stream water quality variables and the three wetland-related principal components were explored through stepwise multiple regression analysis. The proximity of wetlands to the sampling station was related to principal component two, which was associated with decreased annual concentrations of inorganic suspended solids, fecal coliform, nitrates, specific conductivity, flow-weighted NH4 flow-weighted total P, and a decreased proportion of phosphorus in dissolved form(p 〈 0.05). Wetland extent was related to decreased specific conductivity, chloride, and lead concentrations. The wetland-related principal components were also associated with the seasonal export of organic matter, organic nitrogen, and orthophosphate. Relationships between water quality and wetlands components were different for time-weighted averages as compared to flow-weighted averages. This suggests that wetlands were more effective in removing suspended solids, total phosphorus, and ammonia during high flow periods but were more effective in removing nitrates during low flow periods.
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    Biogeochemistry 11 (1990), S. 23-43 
    ISSN: 1573-515X
    Keywords: acid precipitation ; ammonium ; mass balance ; nitrate ; nitrogen ; retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The relative contribution of HN03 to precipitation acidity in eastern Canada has increased in recent years leading to some concern that the relative importance of NO− 3 deposition in acidification of terrestrial and aquatic ecosystems may increase. To gauge the extent of this impact, annual mass balances for N0− 3 and NH+ 4 were calculated for several forested catchments and lakes in Ontario. Retention of NH+ 4 (R NH4) by forested catchments was consistently high compared to retention of NO3 − (R NO3) which was highly variable. Retention of inorganic nitrogen was influenced by catchment grade and areal water discharge. In lakes, the reciprocals of retention of N0− 3 and NH+ 4 were linearly related to the ratio of lake mean depth to water residence time (z/τ; equal to areal water discharge), and retention did not appear to be a function of degree of acidification of the lakes. Net N consumption-based acidification of lakes, defined as the ratio of annual NH; mass to N0− 3 mass consumption, was negatively correlated with /τ and N consumption-related acidification was most likely to occur when − was 〈 1.5 m yr−1. If retention mechanisms are unaffected by changes in deposition, changes in deposition will still result in changes in surface water concentrations although the changes will be of similar proportions. Therefore, ‘NO− 3 saturation’ should not be defined by concentrations alone, but should be defined as decreasing long-term, average NO− 3 retention in streams and lakes in response to long-term increases in NO− 3 deposition. Analysis o f survey data will be facilitated by grouping lakes and catchments according to similar characteristics.
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  • 33
    ISSN: 1573-515X
    Keywords: nitrogen ; snow ; flux
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Increased emissions of nitrogen compounds to the atmosphere by human activities have been well documented. However, in order to better quantify these anthropogenic emissions, better knowledge of natural emissions rates must be known. In addition, variation in natural emissions through time should be documented. In this note we present data collected and/or analyzed by us for NO3 − in recent snow from remote regions of the world. We also summarize existing data sets from other remote regions. This is done to establish a better understanding of NO3 − deposition rates in these regions as well as to add more information to our global understanding of NO3 − deposition.
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    Plant cell, tissue and organ culture 21 (1990), S. 185-189 
    ISSN: 1573-5044
    Keywords: ammonium nitrate ; Malus ; nitrogen ; potassium nitrate ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of some macronutrients, especially NH4NO3 and KNO3, on root development of microcuttings from 3 apple scion cultivars is discussed. A reduction of the level of NH4NO3 in the medium from full strength to 1/4 strength significantly increased the percentage rooting of ‘Gala’ and ‘Royal Gala’, but not ‘Jonagold’. Further reduction of NH4NO3 level from 1/4 strength to zero significantly reduced the percentage of rooting in ‘Gala’ but not ‘Royal Gala’. ‘Jonagold’ rooted best at zero concentration NH4NO3. Without NH4NO3, rooting percentages were as high as 100% for all 3 cultivars when KNO3 was provided at full strength. The results show that adventitious roots can be induced on apple scion cultivars by media manipulation.
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    Biogeochemistry 9 (1990), S. 117-134 
    ISSN: 1573-515X
    Keywords: nitrogen ; Mediterranean ; natural versus anthropogenic atmospheric nitrogen ; atmospheric input ; riverine input ; marine ecosystems ; primary production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Bulk inorganic nitrogen deposition was monitored over a period of 3 years at the Bavella Pass (Corsica, France). Annual fluxes range between 126 and 150μmol.m−2.d-−1, increasing slightly with annual rainfall. Natural background average concentrations of rain water and associated fluxes were estimated from a classification of rain events into ‘natural’ (Oceanic and Saharan), polluted and composite. Long range transport of incoming polluted air masses increases the atmospheric wet nitrogen input by at least a factor of 1.6 in this Mediterranean area. Extrapolation of atmospheric dissolved inorganic nitrogen input to the Western Mediterranean leads to fluxes of 80 to l00μmol.m−2.d-−1. This atmospheric input is in the same order of magnitude as the inorganic nitrogen riverine input. As a consequence, the nitrogen budget for the Mediterranean has had to be reassessed. Atmospheric wet inorganic nitrogen input is of noticeable importance to marine Mediterranean ecosystems, representing on average 10 to 25% of new production in the Western Basin, with values of up to 60% in oligotrophic zones.
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    Ecological research 5 (1990), S. 111-130 
    ISSN: 1440-1703
    Keywords: Big woody materials ; Decomposition rate ; Foothill diperocarp forest ; nitrogen ; turnover time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The dynamics of aboveground big woody organs over 10 cm diameter was studied at a mature foothill dipterocarp forest in West Sumatra. The biomass of big woody organs was estimated to be 519 m3 ha−1 or 408 metric ton ha−1 by means of a pipe model theory. The diameter distribution showed a convex curve and the mode was found at a diameter of about 20 cm. The standing mass of big dead woody litter on the forest floor was 116 m3 ha−1, which accounted for 22% by voume or 9.5% by weight of the biomass of living organs respectively. Thedbh observation with two 1-ha plots for 4 yr and 5 yr respectively revealed that the average net production rate was 9.5 ton ha−1 yr−1. The death rate (7.9 ton ha−1 yr−1) accounted for 83% of the net production rate and was nearly equivalent to the decay rate (7.5 ha−1 yr−1) of dead wood on the forest floor. The balance between the death and decay rates was confirmed for each diameter class. Average turnover periods for big woody organs and dead woody litter were estimated to be 43 and 8.1 yr, respectively. Standing masses of live anddead woody materials accumulated in the study forest were approximately equal to those obtained in a mature tropical lowland rainforest, whereas the flow rates were lower, being only 70% of the corresponding values.
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    Nutrient cycling in agroecosystems 22 (1990), S. 29-35 
    ISSN: 1573-0867
    Keywords: Zinc ; nitrogen ; interaction ; limed ; unlimed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A green house experiment was conducted to study the interaction effect of Zn and N in wheat (S-308). Zinc was applied as ZnSO4.7H2O at 0, 5, 10 and 20 mg per kg, and nitrogen as urea at 0, 75 and 150 mg per kg. In the absence of added N and lime 5 mg Zn per kg increased the grain, straw and root weight, but the application of either N (75 and 150 mg per kg) or lime (4000 mg CaCO3 per kg), 10 mg Zn per kg responded significantly. However, when N and lime were added together, 20 mg Zn per kg increased the grain, straw and root weight significantly. Irrespective of Zn and N, the grain, straw and root weights were higher in limed that in unlimed soils. The application of N increased the Zn concentration in wheat tops and roots in unlimed soils, and decreased it in limed soils. However, because of an increase in wheat yield, the uptake of Zn by wheat tops and roots also increased with N application both in limed and unlimed soils. The addition of Zn to 10 mg per kg, increased the N concentration in the absence of N, but in the presence of N, the addition of Zn to 20 mg per kg decreased the N concentration in wheat tops and roots. The applied Zn to 10 mg per kg in unlimed soils and to 20 mg per kg in limed soils increased the N uptake by wheat tops and roots, respectively. The Zn concentration was higher in absence of lime than in its presence while a reverse trend was true for N concentration.
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  • 38
    ISSN: 1573-0867
    Keywords: Potatoes ; nitrogen ; foliar sprays ; urea ; 15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of the timing of N fertilizer application on the uptake and partitioning of N within the crop and the yield of tubers has been studied in two experiments. In 1985 either none, 8 or 12 g N m−2 was applied and in 1986 none, 12 or 18 g N m−2. Fertilizer N was applied either at planting, around the time of tuber initiation or half at planting and the remainder in four foliar sprays of urea during tuber bulking.15N-labelled fertilizer was applied to measure the recovery of fertilizer N in the crops. There was an apparent pre-emergence loss of nitrate from the soil when N was applied at planting in 1986, thereby reducing the efficiency of fertilizer use. Applying the N at tuber initiation delayed and reduced the accumulation of N in the canopy compared with crops receiving all their fertilizer at planting. Foliar sprays of urea slightly increased both tuber yields and tuber N contents when compared to a single application at planting. The proportion of the fertilizer N recovered in the crop was little affected by the rate of N application, but a greater proportion of foliar-applied N was recovered than N broadcast at planting, due partly to pre-emergence losses of nitrate in 1986. It is suggested that late applications of N was foliar sprays can be of benefit to crops with a long growing season and reduce environmental losses of N.
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    Nutrient cycling in agroecosystems 21 (1990), S. 171-177 
    ISSN: 1573-0867
    Keywords: Bermudagrass ; nitrogen ; model ; nutrient uptake ; forages
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Equations were developed to estimate concentration of nitrogen for bermudagrass forage [Cynodon dactylon, (L.) Pers.] as related to applied nitrogen level and harvest interval. Data from six field studies were used in the analysis. Estimates of N concentration in forage obtained with these equations agreed with data from other studies with fertilizer and waste application to bermudagrass (correlation coefficient of 0.94). Concentration of nitrogen decreased linearly with harvest interval (up to 6 weeks) and increased exponentially with nitrogen level. These equations should provide relevant information for crop production and environmental quality.
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  • 40
    ISSN: 1572-9567
    Keywords: Burnett apparatus ; compressibility factor ; density ; ethane ; methane ; mixtures ; nitrogen ; refractive index ; Z-meter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The European Gas Research Group (GERG; Groupe Européen de Recherches Gazières) initiated a round-robin test of six Z-meters manufactured by Desgranges et Huot, a Burnett apparatus, and an interferometric device to back up the pVT data of the Z-meters. Two gas mixtures were measured. One mixture contained 49.7 mol% of methane and 50.3 mol% of nitrogen; the second mixture 81.3 mol% of methane, 16.4 mol% of ethane, and 2.3 mol% of propane. The test temperatures were mainly 280 and 300 K for the first mixture and 290 and 320 K for the second mixture. The maximum pressures were 8 MPa for Z-meters and 12 MPa for the Burnett apparatus and the grating interferometer. The experimental compressibility factors Z of the six Z-meters are generally in agreement within ±0.05%. The agreement with the reference data from the Burnett apparatus and the refractive index measurements is also within ± 0.05%. Only two isotherms of the binary mixtures differ by about 0.1% from the other data. Recent natural gas measurements show substantially the same results.
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    International journal of thermophysics 11 (1990), S. 201-211 
    ISSN: 1572-9567
    Keywords: enthalpy ; heat capacity ; high temperatures ; nitrogen ; virial coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Calculations of the second virial coefficients and their derivatives for the Hulburt-Hirschfelder (HH) and other accurate interaction potentials are used to determine the thermodynamic properties of nitrogen at high temperatures. Unlike the usual methods employing partition functions, which are most accurate at low temperatures where the energy levels are precisely known, the virial coefficient method depends on integrating over potential energy functions which provide a useful description of energies even near the top of the potential well, a region where the vibrational-rotational energy levels are not readily accessible. This makes this method particularly useful for predicting high-temperature properties outside the range of laboratory measurements and beyond the useful limits of the partition function approach. In the present work, we use the virial coefficient method to predict the heat capacities and enthalpies of nitrogen up to 25,000 K.
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  • 42
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    International journal of thermophysics 11 (1990), S. 597-601 
    ISSN: 1572-9567
    Keywords: measurement techniques ; nitrogen ; parallel-plate apparatus ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A parallel-plate apparatus is suited for accurate measurements of the thermal conductivity coefficient of fluids over a wide range of densities. This is illustrated by measurements of the thermal conductivity coefficient of nitrogen at a temperature of 308.15 K and at pressures up to 20.1 MPa with an accuracy of 0.5%. The agreement with a recent correlation based on accurate measurements by other authors is satisfactory.
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  • 43
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    International journal of thermophysics 11 (1990), S. 897-910 
    ISSN: 1572-9567
    Keywords: binary mixtures ; carbon dioxide ; cylindrical resonator ; electrostatic transducers ; ethane ; gas ; isotherm ; methane ; mixtures ; multicomponent ; mixtures ; natural gas ; nitrogen ; propane ; sound speed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A description of a fixed-path length acoustic resonator which uses electrostatic transducers for sound generation and detection is given. Also, a summary of the measurements on 13 binary and 4 multicomponent gas mixtures of natural gas components is given. Data were obtained at pressures to 10 MPa for five isotherms at 25 K increments from 250 to 350 K. The binary mixtures are primarily methane-rich, with either ethane, nitrogen, carbon dioxide, or propane as the second constituent. The multicomponent mixture compositions represent four naturally occurring natural gas mixtures.
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  • 44
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    Biodegradation 10 (1990), S. 309-328 
    ISSN: 1572-9729
    Keywords: estuaries ; groundwater ; nitrogen ; nitrogen cycle ; nitrogen loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We examined the importance of nitrogen inputs from groundwater and runoff in a small coastal marine cove on Cape Cod, MA, USA. We evaluated groundwater inputs by three different methods: a water budget, assuming discharge equals recharge; direct measurements of discharge using bell jars; and a budget of water and salt at the mouth of the Cove over several tidal cycles. The lowest estimates were obtained by using a water budget and the highest estimates were obtained using a budget of water and salt at the Cove mouth. Overall there was more than a five fold difference in the freshwater inputs calculated by using these methods. Nitrogen in groundwater appears to be largely derived from on site septic systems. Average nitrate concentrations were highest in the region where building density was greatest. Nitrate in groundwater appeared to behave conservatively in sandy sediments where groundwater flow rates were high (〉 11/m2/h), indicating that denitrification was not substantially reducing external nitrogen loading to the Cove. Nitrogen inputs from groundwater were approximately 300 mmol-N/m3/y of Cove water. Road runoff contributed an additional 60 mmol/m3/y. Total nitrogen inputs from groundwater and road runoff to this cove were similar in magnitude to river dominated estuaries in urbanized areas in the United States.
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  • 45
    ISSN: 1573-5087
    Keywords: Lemna gibba ; cytokinins ; isopentenyladenosine ; zeatinriboside ; abscisic acid ; nitrogen ; phosphorus ; relative growth rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The relationship between endogenous cytokinin content and relative growth rate (RGR) was studied in cultures of Lemna gibba L. G3 supplied with daily doses of mineral nutrients that were increased exponentially over time. At the optimal level of nutrient supply the RGR was 30–35% day-1. The RGR was regulated by adjusting the rate of nitrogen supply, or it was restricted by addition of 0.5 μM abscisic acid (ABA). Another approach used to investigate the specific roles of nitrogen (N) and phosphorus (P), was to transfer optimally growing plants to media without N or P but otherwise complete. The plants were harvested at regular intervals for determination of the RGR and levels of cytokinins of the isopentenyladenosine (iPA) and zeatinriboside (ZR) types with an enzyme-linked immunosorbent assay (ELISA). Levels of both iPA- and ZR-type cytokinins decreased when nitrogen was applied to cultures in growth limiting amounts. The cytokinin levels decreased more rapidly than the RGR when either N or P was lacking in the medium, suggesting an early influence of nutrient availability on cytokinin levels which in turn may induce adaptive response by the plant. RGR retardation induced by ABA did not affect cytokinin levels during the first 4 days of the treatment, and the later effects were small. The experiments gave no indication that ABA is involved in the adaptation response of Lemna plants to nutritional stress.
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  • 46
    ISSN: 1573-5117
    Keywords: phytoplankton ; primary production ; phosphorus ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Lake Erken climatic factors such as duration of ice cover, snow-depth and insolation govern the phytoplankton development and the species composition during the spring, with significant variations from year to year. Generally the small diatom, Stephanodiscus hantzschii var. pusillus creates a conspicuous peak at ice-break. In some years motile dinoflagellates start to develop under the ice already in early March, which results in a much longer spring bloom. The highest biomasses were recorded in 1954–1955 with values up to 11 mg 1−1 of fresh weight. The chlorophyll a concentrations have at most reached an epilimnetic average of 30 µg 1−1. The primary production reached a maximum value of 2200 mg C m−2 d−1 in 1955 and the average production for two months during the spring varied from 30 to 64 mg C m−3 d−1. Concerning nutrients, phosphorus was shown to be the limiting nutrient at the end of the spring bloom. This fact was confirmed by orthophosphate concentrations, algal surplus phosphorus content and alkaline phosphatase activity, as well as estimations of inorganic N : P and C : P ratios and nutrient enrichment experiments
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  • 47
    ISSN: 1573-5117
    Keywords: culture ; macroalga ; nitrogen ; nutrition ; seaweed
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seaweeds have physiological mechanisms to acquire, utilize, and store various forms of nitrogen in environments where nitrogen levels vary tremendously in space and time. Knowledge of the nitrogen relationships of seaweeds is required for the development of successful seaweed mariculture. For example, it would seem at first that continuous nitrogen enrichment would be desirable in such systems because maximal seaweed yields are possible only when growth is not nitrogen-limited. Yet such fertilization is wasteful and can result in yield reductions due to the enhancement of epiphyte growth. Because most seaweeds can rapidly taken up high concentrations of nitrogen, far in excess of what is required for current growth demands, enrichments are needed only when internal nitrogen concentrations fall to near the critical level (i.e., the minimal tissue concentration of nitrogen required for maximal growth). Nutrients are best applied at brief pulses of high nitrogen concentrations.
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  • 48
    ISSN: 1573-5117
    Keywords: phosphorus ; alkaline phosphatase activity ; phytoplankton ; Cyanobacteria ; nitrogen ; correspondence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Alkaline phosphatase activity (APA) was investigated monthly for 4 years in the eutrophic Lake Nantua, a lake colonized by a large population of Cyanobacteria. Total enzymatic activity as well as specific activities (the ratios between APA and biomass expressed as dry weight, chlorophyll a, cell phosphorus) varied strongly but they followed a similar pattern during each year. The data were processed using correspondence analysis. Specific APA was never related to depth but highest activities were always associated with low particulate phosphorus and nitrogen, low dissolved inorganic phosphorus (DIP) concentrations, low chlorophyll a to filament number ratio and zero nitrate in the waters, indicating P and N limiting conditions. However a high N/P ratio, close to Redfield optimum also occurred at these conditions. Low activities were associated only with high chlorophyll a to filament number ratio. The results suggest that, during summer P-depletion and as long as the N/P ratio is close or above an optimum value, the DIP enzymatically regenerated from DOP pool by phosphatases could temporarily contribute to the algal phosphorus supply.
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  • 49
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    Plant and soil 128 (1990), S. 115-126 
    ISSN: 1573-5036
    Keywords: ammonium ; mineralization ; nitrate ; nitrification ; nitrogen ; roots ; tomato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tomato root growth and distribution were related to inorganic nitrogen (N) availability and turnover to determine 1) if roots were located in soil zones where N supply was highest, and 2) whether roots effectively depleted soil N so that losses of inorganic N were minimized. Tomatoes were direct-seeded in an unfertilized field in Central California. A trench profile/monolith sampling method was used. Concentrations of nitrate (NO3 -) exceeded those of ammonium (NH4 +) several fold, and differences were greater at the soil surface (0–15 cm) than at lower depths (45–60 cm or 90–120 cm). Ammonium and NO3 - levels peaked in April before planting, as did mineralizable N and nitrification potential. Soon afterwards, NO3 - concentrations decreased, especially in the lower part of the profile, most likely as a result of leaching after application of irrigation water. Nitrogen pool sizes and rates of microbial processes declined gradually through the summer. Tomato plants utilized only a small percentage of the inorganic N available in the large volume of soil explored by their deep root systems; maximum daily uptake was approximately 3% of the soil pool. Root distribution, except for the zone around the taproot, was uniformly sparse (ca. 0.15 mg dry wt g-1 soil or 0.5 cm g-1 soil) throughout the soil profile regardless of depth, distance from the plant stem, or distance from the irrigation furrow. It bore no relation to N availability. Poor root development, especially in the N-rich top layer of soil, could explain low fertilizer N use by tomatoes.
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  • 50
    ISSN: 1573-5036
    Keywords: anaerobic soils ; bacterial flush ; mineralisation ; nitrification ; nitrogen ; restoration ; soil perfusion ; soluble carbon ; stockpiles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Topsoil stockpiled for 4 years resulted in an accumulation of NH4-N at depths of 1m or more in mound, as measured by an ammonia gas-sensing electrode. When leached with water these soils were also found to contain high concentrations of dissolved organic C below 1m. Both NH4-N and DOC were products of microbial mineralisation of soil organic matter that accumulated under anaerobic conditions. When these soils were restored a flush of decomposition took place, fuelled by labile organic matter and soluble nitrogen. Stockpiled soil which underwent an ammonium-rich perfusion regime in the laboratory indicated that in-mound soils rapidly attained greater nitrification potential than surface mound soils and also had greater potential for further mineralisation of organic matter to NH4-N. This further production was seen as a contribution from the bacterial flush, stimulated by the large labile-C pool already present. As the bulk of stored soil was anaerobic, restored soils were seen as potentially wasteful of their N-reserves; the fate of nitrogen and soluble carbon compounds in restored soils is discussed.
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  • 51
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    Plant and soil 129 (1990), S. 219-225 
    ISSN: 1573-5036
    Keywords: drying ; grassland ; heating ; microbial biomass ; mineralization ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A dwarf bamboo-type grassland soil (Thick High-humic Andosol) was nitrogen-limited for grass despite the presence of a considerable amount of microbial biomass N. By either treatments of air-drying and subsequent heating, the content of mineral N in the soil was increased by 3.7 g N and 11.7 g N m-2, respectively, after a 55-day incubation period. The efficiency of mineralized N for growth of orchardgrass was compared with nitrate-N added just before cultivation. The dry matter content of the grass increased from 81.7 g (control) to 169 g and to 337 g m-2 in the dried and in the heated soils, respectively, when N application was omitted. Of the mineral N released by air-drying and heating of the soil, 84% and 77% were absorbed by the grass, and 30% and 20% was assumed to be derived from microbial biomass, respectively. In contrast the grass apparently absorbed 54–56% of the 5 g nitrate-N m-2 added to the control and the air-dried soils. It was also noted that fungal biomass N had decreased by 1.5–1.9 g m-2 in the control soil after addition of 10 g nitrate-N m-2.
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  • 52
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    Biogeochemistry 10 (1990), S. 1-28 
    ISSN: 1573-515X
    Keywords: boreal forest ; decomposition ; litter quality ; nitrogen ; productivity ; soil temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A model of boreal forest dynamics was adapted to examine the factors controlling carbon and nitrogen cycling in the boreal forests of interior Alaska. Empirical relationships were used to simulate decomposition and nitrogen availability as a function of either substrate quality, the soil thermal regime, or their interactive effects. Test comparisons included black spruce forests growing on permafrost soils and black spruce, birch, and white spruce forests growing on permafrost-free soils. For each forest, simulated above-ground tree biomass, basal area, density, litterfall, moss biomass, and forest floor mass, turnover, thickness, and nitrogen concentration were compared to observed data. No one decay equation simulated forests entirely consistent with observed data, but over the range of upland forest types in interior Alaska, the equation that combined the effects of litter quality and the soil thermal regime simulated forests that were most consistent with observed data. For black spruce growing on permafrost soils, long-term simulated forest dynamics in the absence of fire resulted in unproductive forests with a thick forest floor and low nitrogen mineralization. Fires were an important means to interrupt this sequence and to restart forest succession.
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