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  • nitrogen  (100)
  • Springer  (100)
  • Cell Press
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
  • 2015-2019
  • 2005-2009
  • 1990-1994  (100)
  • 1992  (51)
  • 1990  (49)
Collection
Publisher
  • Springer  (100)
  • Cell Press
  • Essen : Verl. Glückauf
  • Krefeld : Geologischer Dienst Nordhein-Westfalen
Years
  • 2015-2019
  • 2005-2009
  • 1990-1994  (100)
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  • 1
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    Entomologia experimentalis et applicata 64 (1992), S. 225-238 
    ISSN: 1570-7458
    Keywords: Lymantria dispar (L.) ; diet switching ; nitrogen ; specialization ; plant-animal interactions ; insect behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gypsy moth (Lymantria dispar (L.) (Lepidoptera: Lymantriidae)) larvae were reared from hatch on 1.25% N or 3.5% N artificial diet (previous diet) and switched reciprocally to the other diet (current diet) after molting into the second, third, fourth, or fifth instar. The nitrogen concentration of food consumed during previous instars had a strong residual effect on the growth rate in subsequent instars when a diet switch was made during instars two through four, but did not affect growth rate of fifth-instar larvae despite effects on food consumption and utilization. In early instars, larvae reared on 1.25% N artificial diet and then switched to 3.75% N diet had lower mass-adjusted growth rates than larvae continuously reared on 3.75% N diet. Conversely, larvae reared on 3.75% N diet and switched to 1.25% N had higher mass-adjusted growth rates than larvae reared continuously on 1.25% N diet. Relative to larvae previously reared on 1.25% N diet, fifth-instar male larvae previously reared on 3.75% N diet had slightly lower consumption rates, higher net growth efficiency (ECD), and higher gross growth efficiency (ECI). Larvae previously reared on 3.75% N diet tended to have lower food assimilation efficiency (AD) and lower nitrogen assimilation efficiency (AD(N)). Although both previous and current diet nitrogen concentration strongly affected larval growth and food utilization, the interaction term between these was not significant for any response variables except ECD and ECI. Because the interaction term reflects the effect of switching per se, the results indicate that there was a metabolic cost associated with switching, but no inherent net cost or benefit of diet-switching to growth.
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  • 2
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    Catalysis letters 13 (1992), S. 45-53 
    ISSN: 1572-879X
    Keywords: Ammonia ; synthesis ; nitrogen ; rate-determining step ; potassium promotion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The simple concept of a single rate-determining step, the dissociation of N2(a), in ammonia synthesis is inconsistent with experimental results. It is proposed that three reaction steps, N2(a) → 2N(a) (1) N(a) + H(a)→NH(a) (2) NH3(a)→NH3(g) (3) are dominant in determining the rate of synthesis. Under industrial conditions reactions (2) and (3) are more important than (1). The role of K+ as promoter in these reactions is discussed, especially as an “anchor” for adsorbed oxygen.
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  • 3
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    Catalysis letters 16 (1992), S. 159-164 
    ISSN: 1572-879X
    Keywords: Chemisorption ; nitrogen ; carbon dioxide ; platinum ; water gas shift reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The relationship between sites responsible for nitrogen chemisorption and sites responsible for stronger adsorption of carbon dioxide on platinum black is reported. A 2 to 1 ratio has been found between molecules of more strongly adsorbed carbon dioxide and molecules of nitrogen chemisorbed on individual samples. This relationship has allowed us to deduce the structure of chemisorbed carbon dioxide. Carbon dioxide is relatively weakly chemisorbed on platinum. Reasons for the weakness of this chemisorption are discussed.
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  • 4
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    Entomologia experimentalis et applicata 62 (1992), S. 29-36 
    ISSN: 1570-7458
    Keywords: Alkaloids ; cinnabar moth ; insect genetics ; larval performance ; Lepidoptera ; nutritional ecology ; nitrogen ; sugar ; Tyria jacobaeae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a laboratory experiment using full-sibs, 60% of the variation in pupal weight of the monophage Tyria jacobaeae L. (Lepidoptera, Arctiidae) could be explained by variation in the nitrogen concentration of the food plant, Senecio jacobaea L. and only 4% by variation in sugar concentration. Larval weight and growth rates of young and old larvae were also positively correlated with nitrogen and sugar concentration. Developmental time was negatively correlated with nitrogen concentration. In a second experiment full-sib families differed significantly in larval weight at day 7, mortality, growth rate and developmental time. Pupal weight did not differ significantly among families, but was positively correlated with nitrogen concentration of Senecio. Larval performance was not significantly influenced by concentrations of sugars or alkaloids. We conclude that larval performance of Tyria during most of the larval period is mainly determined by genetic factors, but pupal weights are primarily determined by nitrogen concentration of the food plant.
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  • 5
    ISSN: 1573-0867
    Keywords: Wheat ; nitrogen ; grain protein content ; grain filling ; urea spraying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this work was to determine the effect of foliar urea spraying during or after anthesis, on dry matter and nitrogen accumulation in the wheat grain of two cultivars, differing in grain protein content. The experiment was carried out in the field, and 20 kg N ha−1 as urea (46-0-0) was sprayed at anthesis, 7 or 14 days after anthesis. Dry weight, N content and N percentage of the grain were determined at several stages of its development. Neither the rate nor the duration of dry matter accumulation in the grain was significantly modified by N sprayings at anthesis or later and, consequently, not its final weight. Nitrogen sprayings at anthesis or later increased the grain N content and N percentage at ripeness in both cultivars, but to a greater extent in the low grain protein cultivar. Greater N content in the grain was attributed to a rapid uptake of the N applied and not to a longer duration of the period of N accumulation. The different responses of the cultivars to N sprayings can be related to differences in N demand, and is probably associated, also, to a genetic ability to accumulate N in the grain.
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  • 6
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    Nutrient cycling in agroecosystems 32 (1992), S. 55-59 
    ISSN: 1573-0867
    Keywords: 15N ; nitrogen ; rice ; soil N ; N fertilizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the southern U.S. rice belt it is recommended that rice (Oryza sativa L.) grown in the dry-seeded, delayed flood cultural system have the preflood N fertilizer applied and the field flooded at the fourth to fifth leaf stage of plant development. The objective of this field study was to determine if delaying the flood and preflood N application past the fifth leaf stage was detrimental to rice total N and fertilizer15N uptake, total dry matter, and grain yield. This study was conducted on a Crowley silt loam (Typic Albaqualfs) and a Perry clay (Vertic Haplaquepts). The preflood N fertilizer and flood were delayed 0, 7, 14, or 21 d past the fourth to fifth leaf stage, after which time a permanent flood was established and maintained until maturity. All treatments received 20.5 g N m−2 as15N-labeled urea in three topdress applications. All plant and soil samples were taken at maturity. Harvest index increased as the preflood N and flood were delayed past the 4 to 5 leaf stage. Total N in the grain + straw either decreased or showed a decreasing trend as the N and flood were delayed. Similarly, uptake of native soil N decreased as flood was delayed. Conversely, percent recovery of fertilizer N in the rice plant and the plant-soil system increased as the preflood N and flood were delayed. Rice grain yield was not significantly affected by delaying the preflood N and flood up to 21 d.
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  • 7
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    Aquatic sciences 54 (1992), S. 58-76 
    ISSN: 1420-9055
    Keywords: Eutrophication ; lake management ; phosphorus ; nitrogen ; chlorophyll-a ; slope estimator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We estimate the response of chl-a (mg · m−3) to changes in concentrations of total phosphorus (TP) by calculating the slopeS = Δchl-a/ΔTP in chl-a =f(TP) graphs. Results show that in years where algae are P-limited oligotrophic lakes respond less (median slope 0.21) to changes in nutrient concentrations than eutrophic lakes, (median slope 0.31) and these again less than hypereutrophic lakes, (median slope 1.02). We find no saturation value for the slope within the TP range considered (6–480 mg · m−3). Chl-a in eutrophic lakes responds more frequently to non-nutrient factors than oligotrophic and hypereutrophic lakes. Results obtained by replacing TP with a new nutrient parameter, TP′ = 0.056 · TP · IN0.226, in which inorganic nitrogen, IN, is factored in, suggest that nitrogen has an influence on chl-a in oligotrophic lakes. Blue-green algae respond less to changes in TP than other algal species, e.g., diatoms.
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  • 8
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    Potato research 35 (1992), S. 355-364 
    ISSN: 1871-4528
    Keywords: cultivar ; nitrate ; nitrogen ; Solanum tuberosum L. ; tuber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The duration of dormancy of seed potatoes varies between years and between origins. Therefore, the effects of conditions during crop growth on dormancy of progeny tubers were studied. The effect of nitrogen during tuber bulking on the duration of dormancy was investigated in three field experiments with two cultivars. In addition to an application of 125 kg N/ha at planting, top dressings of 0–150 kg N/ha were given about 2 weeks after tuber initiation. Haulm was pulled about 4 weeks later. The effect of nitrogen rate at planting was also examined in one experiment. Nitrogen top dressings shortened dormancy in all experiments by 5–8 days. An increased nitrogen rate at planting resulted in a shorter dormancy when the duration of dormancy was expressed in days after tuber initiation, but not when it was expressed in days after haulm pulling, probably because extra nitrogen also delayed tuber initiation.
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  • 9
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    Potato research 35 (1992), S. 365-375 
    ISSN: 1871-4528
    Keywords: cultivar ; heat sprouting ; nitrogen ; second growth ; Solanum tuberosum L. ; sprout ; tuber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In two indoor experiments under short day conditions, the effect of temperature during tuber bulking on dormancy of tubers was investigated for cvs Diamant and Désirée. Temperature treatments started after tuber initiation and lasted for 4 weeks, after which the haulm was removed. In Experiment 1, the day/night temperature regimes 18/12, 22/22, 26/18 and 32/12 °C (T18/12 etc.) were compared. In Experiment 2, three day temperatures (18, 24 and 30 °C) were combined with three night temperatures (12, 18 and 24 °C), resulting in nine treatments. The dormancy of cv. Diamant was shortest after very high day temperatures (30–32 °C), but intermediate day temperatures (22–26 °C) had no shortening effect compared to T18/12. Dormancy of cv. Désirée was not shortened, but rather tended to be prolonged by high temperatures (22–32 °C) during growth. High temperatures during growth resulted in more sprouts per tuber after dormancy had ended.
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  • 10
    ISSN: 1573-5176
    Keywords: amino acids ; biomass ; fatty acids ; Isochrysis ; nitrogen ; starvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth of cells ofIsochrysis galbana with either nitrate or ammonium as the N-source, and the effects of subsequent N-starvation of these cells, were compared. During exponential N-sufficient growth nitrate-grown cells had double the fatty acid content of the ammonium-grown cells but lower concentrations of a few amino acids. Following resuspension in N-free medium the fatty acid content of the ammonium-grown cells increased to that of the nitrate-grown cells, but there was no further increase in fatty acid content on a C-biomass or cellular basis during the following 4 days for either culture. Fatty acid synthesis was continuous during N-starvation, while it occurred during the light-phase only in exponential growth. The proportion of 18:1n9 fatty acid increased from 10 to 25% total fatty acids during N-starvation. Intracellular free amino acid content decreased in a similar manner in both cultures on N-starvation, the ratio of intracellular free amino-N/cell-C falling more rapidly than overall cellular N/C. It was concluded that optimal amino acid and fatty acid content would be attained by growth in the presence of excess nitrate. Measurements of chlorophyll and carotenoid content and ofin vivo fluorescence indicated that these parameters had potential for monitoring the C and N biomass in cultures grown under relatively constant (not necessarily continuous) illumination.
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  • 11
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    Plant and soil 139 (1992), S. 285-294 
    ISSN: 1573-5036
    Keywords: Brassica ; B. campestris ; B. carinata ; B. juncea ; B. naptus ; B. nigra ; B. oleracea ; calcium ; chloride ; potassium ; magnesium ; nitrogen ; sodium ; nutrients ; salinity ; salt-tolerance ; seawater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The growth of six rapid-cycling lines of Brassica species, B. napus, B. campestris, B. nigra, B. juncea, B. oleracea and B. carinata was inhibited by seawater salinity. Based on the change in dry matter reduction relative to the control at varying concentrations of salts (4, 8 and 12 dS m-1), the relative salt tolerance of these species was evaluated. B. napus and B. carinata were the most tolerant and most sensitive species, respectively, while the other four species were moderately tolerant. The influence of seawater on the concentrations of 12 elements including macronutrients and micronutrients in the shoots of these Brassica plants was characterized to determine the relationship between nutritional disturbance and relative salt tolerance. It was found that seawater salinity had a significant effect on the concentrations of Ca, Mg, K, Cl, Na and total N in the shoots of these plants but only the change in Ca concentration was significantly related to the relative salt tolerance of these six rapid-cycling Brassica species according to a rank analysis of the data. This finding indicates that Ca may play a regulatory role in the responses of Brassica species to saline conditions.
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  • 12
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    Plant and soil 142 (1992), S. 157-166 
    ISSN: 1573-5036
    Keywords: Acacia ; Eucalyptus regnans ; decomposition ; litterfall ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The N and P contents of the litter layer and the return of these nutrients in litterfall were measured in seven stands of Mountain Ash (Eucalyptus regnans) ranging in age from 5 years to about 250 years. Both annual litterfall and nutrient return were correlated with stand basal area and were high compared with other productive eucalypt forests. In contrast, the fall of dead eucalypt leaves was constant with stand age, demonstrating that sites are fully occupied at an early age. Similarly, amounts of N and P in total leaf fall (overstorey plus understorey) were constant with stand age, except for low amounts in the stand aged 40 years where Acacia spp., important fixers of atmospheric N, were not prevalent. The decomposition constant (k) of organic matter in the litter layer decreased with stand age, from 0.31 year-1 at age 5 years to 0.23 year-1 at age 250 years. These constants also applied to N and P, indicating a tight coupling between organic matter decomposition and release of these nutrients from litter. The litter layer released about 30 kg ha-1 of N at age 5 years, and about 70 kg ha-1 at age 80 years. These results are discussed in relation to growth of Mountain Ash following fire, and the subsequent retention and accumulation of N during stand development.
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  • 13
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    Plant and soil 142 (1992), S. 167-176 
    ISSN: 1573-5036
    Keywords: Eucalyptus regnans ; mineralization ; nitrification ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory and in situ rates of N mineralization in soils from Mountain Ash (Eucalyptus regnans) forests were measured fortnightly for two years in stands aged 9, 40, 80 and about 250 years (overmature), and for one year in stands aged 5 and 46 years. Rates of anaerobic mineralization (the laboratory test) showed little seasonal or annual variation. In contrast, rates of in situ mineralization varied markedly with season, being highest in spring and summer. Anaerobic mineralization was highly correlated with stand age to 80 years, but decreased between ages 80 and 250 years. In situ mineralization also decreased between these two ages, but otherwise was not related to stand age. Hence, the correlation between anaerobic and in situ mineralization along the age sequence was weak, suggesting that the anaerobic test is of maximum utility when this pool is in balance with inputs from decomposing litter (‘steady-state’ ecosystems). Nitrification was strong in stands aged 9, 46, 80 and 250 years and weak in stands aged 5 and 40 years. Within stands, the rate of nitrification during each period of in situ containment was highly dependent on the supply of NH4 ions. Between stands, annual rates of nitrification appear to be related to the balance between the N capital of the site, its rate of turnover, and the demand for N by heterotrophs and vegetation so that if NH4 supply is depleted, little is left for autotrophic nitrifiers.
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  • 14
    ISSN: 1573-5036
    Keywords: ammonium ; citrus ; nitrate ; NO3 −/NH4 + ratio ; nitrogen ; nutrient solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In short-term water culture experiments with different 15N labeled ammonium or nitrate concentrations, citrus seedlings absorbed NH4 + at a higher rate than NO3 −. Maximum NO3 − uptake by the whole plant occurred at 120 mg L−1 NO3 −-N, whereas NH4 + absorption was saturated at 240 mg L−1 NH4 +-N. 15NH4 + accumulated in roots and to a lesser degree in both leaves and stems. However, 15NO3 − was mostly partitioned between leaves and roots. Adding increasing amounts of unlabeled NH4 + (15–60 mg L−1 N) to nutrient solutions containing 120 mg L−1 N as 15N labeled nitrate reduced 15NO3 − uptake. Maximum inhibition of 15NO3 − uptake was about 55% at 2.14 mM NH4 + (30 mg L−1 NH4 +-N) and it did not increase any further at higher NH4 + proportions. In a long-term experiment, the effects of concentration and source of added N (NO3 − or NH4 +) on nutrient concentrations in leaves from plants grown in sand were evaluated. Leaf concentration of N, P, Mg, Fe and Cu were increased by NH4 + versus NO3 − nutrition, whereas the reverse was true for Ca, K, Zn and Mn. The effects of different NO3 −-N:NH4 +-N ratios (100:0, 75:25, 50:50, 25:75 and 0:100) at 120 mg L−1 total N on leaf nutrient concentrations, fruit yield and fruit characteristics were investigated in another long-term experiment with plants grown in sand cultures. Nitrogen concentrations in leaves were highest when plants were provided with either NO3 − or NH4 + as a sole source of N. Lowest N concentration in leaves was found with a 75:25 NO3 −-N/NH4 +-N ratio. With increasing proportions of NH4 + in the N supply, leaf nutrients such as P, Mg, Fe and Cu increased, whereas Ca, K, Mn and Zn decreased. Yield in number of fruits per tree was increased significantly by supplying all N as NH4 +, although fruit weight was reduced. The number of fruits per tree was lowest with the 75:25 NO3 −-N:NH4 +-N ratio, but in this treatment fruits reached their highest weight. Rind thickness, juice acidity, and colour index of fruits decreased with increasing NH4 + in the N supply, whereas the % pulp and maturity index increased. Percent of juice in fruits and total soluble solids were only slightly affected by NO3 −:NH4 + ratio.
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  • 15
    ISSN: 1573-5044
    Keywords: carbohydrate ; germination ; Impatiens L. ; Impatiens platypetala L. ; nitrogen ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In vitro germination of 20-day old immature ovules of Impatiens platypetala Lindl. was inhibited at concentrations as low as 50 mM sucrose or mannitol and 100 mM glucose. Younger ovules (12, 14, and 16 days old) were similarly inhibited at 100 mM sucrose. Inorganic nitrogen concentration did not affect germination regardless of ovule age, but seedling fresh weight was significantly less and abnormal development of seedlings was significantly increased by total inorganic nitrogen concentrations higher or lower than 30 mM (at a ratio of 20: 10 mM NO3 -: NH4 +) in the culture medium.
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  • 16
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    Plant and soil 139 (1992), S. 247-251 
    ISSN: 1573-5036
    Keywords: ammonium ; lupins ; nitrate ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two cultivars of Lupinus angustifolius L. were grown in a glasshouse in solutions containing NO3 -, NH4 + or NH4NO3 with a total nitrogen concentration of 2.8 M m-3 in each treatment. One cultivar chosen (75A-258) was relatively tolerant to alkaline soils whereas the other (Yandee) was intolerant to alkalinity. Controlled experiments were used to assess the impact of cationic vs. anionic forms of nitrogen on the relative performance of these cultivars. Relative growth rates (dry weight basis) were not significantly different between the two cultivars when grown in the presence of NO3 -, NH4 + or NH4NO3. However, when NO3 - was supplied, there was a modest decline in relative growth rates in both cultivars over time. When plants grown on the three sources of nitrogen for 9 days were subsequently supplied with 15NH4NO3 or NH4 15NO3 for 30 h, NH4 + uptake was generally twice as fast as NO3 - uptake, even for plants grown in the presence of NO3 -. Low rates of NO3 - uptake accounted for the decrease in growth rates over time when plants were grown in the presence of NO3 -. It is concluded that the more rapid growth of 75A-258 than Yandee in alkaline conditions was not due to preferential uptake of NH4 + and acidification of the external medium. In support of this view, acidification of the root medium was not significantly different between cultivars when NH4 + was the sole nitrogen source.
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  • 17
    ISSN: 1573-5036
    Keywords: critical concentration ; deficiency ; diagnosis ; growth rate ; lettuce ; luxury consumption ; nitrogen ; nitrate ; nutrient requirement ; petiole sap ; phosphorus ; phosphate ; potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A method is described for determining the way in which growth rate varies with plant nutrient concentration using a simple nutrient interruption technique incorporating only 2 treatments. The method involves measuring the changes in growth and nutrient composition of otherwise well-nourished plants after the supply of one particular nutrient has been withheld. Critical concentrations are estimated from the relationship between the growth rate (expressed as a fraction of that for control plants of the same size which remained well-nourished throughout) and the concentration of the growth-limiting nutrient in the plants as deficiency developed. Trials of the method using young lettuce plants showed that shoot growth rate was directly proportional to total N (nitrate plus organic N) concentration, and linearly or near-linearly related to K and P concentration over a wide range; the corresponding relationship for nitrate was strongly curvi-linear. Critical concentrations (corresponding to a 10% reduction in growth rate) determined from these results were similar to critical values calculated from models derived from field data, but were generally higher than published estimates of critical concentration (based on reductions in shoot weight) for plants of a similar size. Reasons for these discrepancies are discussed. Nitrate, phosphate or potassium concentrations in sap from individual leaf petioles were highly sensitive to changes in shoot growth rate as deficiency developed, with the slope of the relationships varying with leaf position, due to differences both in their initial concentration and in the rates at which they were utilized in individual leaves. Each nutrient was always depleted more quickly in younger leaves than in older ones, providing earlier evidence of deficiency for diagnostic purposes. Although the plants were capable of accumulating nitrate, phosphate and potassium well in excess of that needed for optimum dry matter production during periods of adequate supply, the rate of mobilization of these reserves was insufficient to prevent reductions in growth rate as the plants became deficient. This brings into question the validity of the conventional concept that luxury consumption provides a store of nutrients which are freely available for use in times of shortage. The implications of these results for the use of plant analysis for assessing plant nutrient status are discussed.
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  • 18
    ISSN: 1573-5036
    Keywords: Alternaria alternata ; black point ; fertilization ; irrigation ; nitrogen ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Agronomic studies were conducted to examine the effect of fertilizer N on black point incidence in Fielder soft white spring wheat (Triticum aestivum L. em Thell.). Black point incidence rose with increases in the amount of N supplied either as fertilizer applied during the growing season in irrigation water or as soil N, specifically nitrate, from fertilizer N application in previous years. A comparison of four different irrigation regimes demonstrated that black point incidence was highest under frequent irrigation (irrigate to field capacity at 75% available moisture) and lowest under conventional irrigation (irrigate to field capacity at 50% available soil moisture). In each irrigation regime, disease incidence increased as N rates were raised from 0 to 120 kg ha-1. A residual fertilizer-N study demonstrated in 1985 and 1986 that black point incidence generally rose with increasing levels of nitrogen from either preplant applications in the spring or soil nitrate from the previous year. However, additions of fertilizer N were shown to slightly reduce black point incidence at soil nitrate levels above 150 kg ha-1. A two-year fertilizer N study demonstrated that in treatments receiving the same amount (90 kg ha-1) of fertilizer N, the amount broadcast as a preplant treatment versus the amount applied in irrigation water in a fertigation treatment had no effect on black point incidence, but all fertilized treatments had significantly higher levels of disease than the unfertilized check.
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  • 19
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    Plant and soil 142 (1992), S. 19-30 
    ISSN: 1573-5036
    Keywords: barley ; fertilizer ; green manure ; legume ; lentil ; nitrogen ; non-nutritional response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Green manure application may benefit subsequent crops not only by improving nitrogen (N) fertility but also via non-nutritional mechanisms. The quantification of the latter effect, however, is complicated by the confounding effect of N fertility. Two experiments were conducted in controlled environments to partition the yield response of barley to green manure between N and non-nutritional effects. Each experiment included a factorial of fertilizer N application rates and green manure application rates. The fertilizer was labelled with 15N to facilitate discrimination between N sources. Approximately 24% of the N applied in green manure was assimilated by barley after 45 days (Experiment 1) and 32% was recovered by barley grown to maturity (Experiment 2). Apparent recovery of green manure-N by barley was not appreciably affected by fertilizer application. Regression analysis of the relationship between dry matter yield and plant N uptake demonstrated that yield responses to green manure application were not entirely attributable to improved N fertility. For a given amount of N assimilated by the crop, yields were higher in green manure-amended treatments than in those receiving no green manure. In barley grown to maturity, barley response to N and non-nutritional effects were estimated to be 5.3 and 2.2g pot−1, respectively. The relationship between dry matter yield and N uptake is suggested as a method for distinguishing nutritional and non-nutritional yield responses. This approach assumes that no other nutrient is limiting growth. The presence of non-nutritional benefits observed in this study demonstrates that the agronomic value of green manure is not limited to N release and casts doubt on the assumptions inherent to calculation of fertilizer equivalents.
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  • 20
    ISSN: 1573-5036
    Keywords: mineralization capacity ; nitrogen ; principal components analysis ; soil incubation ; temperate humid zone ; soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The N mineralization capacity of 41 temperate humid-zone soils of NW Spain was measured by aerobic incubation for 15 days at 28°C and 75% of field capacity. The main soil factors affecting organic N dynamics were identified by principal components analysis. Ammonification predominated over nitrification in almost all soils. The mean net N mineralization rate was 1.63% of the organic N content, and varied according to soil parent materials as follows: soils on basic and ultrabasic rocks 〈 soils over acid metamorphic rocks 〈 soils developed over sediments 〈 soils over acid igneous rocks 〈 soils on limestone. The N mineralization capacity was lower in natural soils than in cropped soils or pastures. The accumulation of organic matter (C and N) seems to be due to poor mineralization which was caused, in decreasing order of importance, by high exchangeable H-ion levels, high Al and Fe gel contents and, to a lesser extent (though more markedly in cropped soils), by silty clay texture and exchangeable Al ions.
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  • 21
    ISSN: 1573-5036
    Keywords: cultivars ; grains ; maize ; nitrogen ; phosphorus ; potassium ; tropical climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An earlier study revealed considerable genotypic variation in grain N, P and K concentrations (GNC, GPC and GKC, respectively) in tropical maize. The expression of varietal differences in GNC, GPC and GKC, however, may depend on environmental conditions such as the N status of the soil. Two tropical maize hybrids (Suwan 2301 and CP 1) with comparable yielding capacity, but contrasting GNCs, GPCs and GKCs, were therefore grown at four levels of N in a field experiment at Farm Suwan (Thailand, latitude 14.5°N). Suwan 2301 exhibited a higher GNC than did CP 1 at all rates of N, but large differences in GPC and GKC were found only at high N fertilization. This was obviously due to individual grain yield responses of the cultivars to increasing rates of N fertilizer, demonstrating that grain nutrient concentrations are, at least in part, functions of the amount of grain carbohydrates which dilute a genetically and environmentally fixed amount of grain P and K. As compared to Suwan 2301, CP 1 accumulated less N, P and K in the grains at almost all levels of N fertilization, confirming our hypothesis that the cultivation of maize genotypes with low grain mineral nutrient concentrations may help third-world cash-crop farmers to reduce the need for scarce and costly mineral fertilizers. This finding has to be verified at reduced availability of soil −P, −K, and water.
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  • 22
    ISSN: 1573-5036
    Keywords: abiotic factors ; ectorganic layer ; forest ; mineralization ; moisture ; nitrification ; nitrogen ; pH ; regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The relationships between nitrogen transformations and moisture and pH in coniferous forest litter were determined using laboratory incubation experiments. A linear relation between gravimetric moisture content and nitrification was found within the whole studied range of moisture conditions (10–290% ODW). Net nitrogen mineralization increased linearly with moisture content up to 140% ODW. At higher moisture contents, net mineralization was found to be independent of moisture. Relative nitrification was found to be a linear function of moisture content. The dependence of the CO2 production rates on moisture in the coniferous litter decreased from low to high moisture availability. Due to a nearly linear relationship between gravimetric moisture content and log-(water potential) within the investigated moisture range, the same type of relationships were found with this latter parameter as well. The relationship between nitrogen transformations and pH was studied by means of the addition of different amounts of HCl and NaOH during short incubation experiments (1 week). Nitrification was found to be a negative linear function of the H-ion concentration within the range of 0.04 (pH 4.40) and 0.36 (pH 3.45) mmol H-ion L−1. At a higher H-ion concentration and thus at a lower pH than 3.45, no nitrate was produced any more. No relationship between net mineralization and pH was found.
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  • 23
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    Plant and soil 139 (1992), S. 253-263 
    ISSN: 1573-5036
    Keywords: carbon ; exudation ; mineralisation ; nematode ; nitrogen ; protozoa ; rhizosphere ; root ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The possibility is examined that carbon (C) released into the soil from a root could enhance the availability of nitrogen (N) to plants by stimulating microbial activity. Two models are described, both of which assume that C released from roots is used by bacteria to mineralise and immobilise soil organic N and that immobilised N released when bacteria are grazed by bacterial-feeding nematodes or protozoa is taken up by the plant. The first model simulates the individual transformations of C and N and indicates that root-induced N mineralisation could supply only up to 10% of the plant's requirement, even if unrealistically ideal conditions are assumed. The other model is based on evidence that about 40% of immobilised N is subsequently taken up by the plant. A small net gain of N by the plant is shown (i.e. the plant takes up more N than it loses through exudation), although with exudate of up to C:N 33:1 less than 6% of the plant's requirement is supplied by root-induced N mineralisation. It is argued, however, that rhizosphere bacteria do not use plant-derived C to mineralise soil organic N to any great extent and that in reality root-induced N mineralisation is even less important than these models indicate.
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  • 24
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    Plant and soil 141 (1992), S. 57-67 
    ISSN: 1573-5036
    Keywords: aquatic legumes ; Azolla ; Cyanobacteria ; flooded rice soils ; nitrogen ; N2 fixation ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper summarizes recent achievements in exploiting new biological nitrogen fixation (BNF) systems in rice fields, improving their management, and integrating them into rice farming systems. The inoculation of cyanobacteria has been long recommended, but its effect is erratic and unpredictable. Azolla has a long history of use as a green manure, but a number of biological constraints limited its use in tropical Asia. To overcome these constraints, the Azolla-Anabaena system as well as the growing methods were improved. Hybrids between A. microphylla and A. filiculoides (male) produced higher annual biomass than either parent. When Anabaena from high temperature-tolerant A. microphylla was transferred to Anabaena-free A. filiculoides, A. filiculoides became tolerant of high temperature. Azolla can have multiple purposes in addition to being a N source. An integrated Azolla-fish-rice system developed in Fujian, China, could increase farmers' income, reduce expenses, and increase ecological stability. A study using Azolla labeled with 15N showed the reduction of N losses by fish uptake of N. The Azolla mat could also reduce losses of urea N by lowering floodwater-pH and storing a part of applied N in Azolla. Agronomically useful aquatic legumes have been explored within Sesbania and Aeschynomene. S. rostrata can accumulate more than 100kg N ha-1 in 45 d. Its N2 fixation by stem nodules is more tolerant of mineral N than that by root nodules, but the flowering of S. rostrata is sensitive to photoperiod. Aquatic legumes can be used in rainfed rice fields as N scavengers and N2 fixers. The general principle of integrated uses of BNF in rice-farming systems is shown.
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  • 25
    ISSN: 1573-5117
    Keywords: River Rhine ; phytoplankton ; suspended material ; carbon ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial and temporal distribution of element concentrations were monitored together with chlorophyll a as an indicator of algal density to assess the effect of phytoplankton on the elemental composition (C, N, P) of suspended materials in the lower Rhine. The high concentrations of particulate C, N and P in the river were found to decrease in the delta and to increase again in the estuarine turbidity zone. Phytoplankton blooms increased the concentrations of particulate C, N, and P significantly in the upstream part of the river. In summer 1989, 15–65% of the particulate C and 20–75% of the particulate N were attributable to phytoplankton. Together with published data these observations indicate that in eutrophic rivers, the input of organic materials from the catchment is strongly modified and supplemented by in situ growth of phytoplankton. During seaward transport the phytoplankton and the particulate elements disappeared from the river water concomitantly with the suspended matter, indicating an increased retention of these elements due to sedimentation. In contrast, soluble ammonia, nitrite and phosphate increased in the tidal reaches of the river because of local input in the harbour and city of Rotterdam and because of mineralization. Therefore the total nutrient load of the Rhine estimated at the German/Dutch border does not reflect the actual input into the sea.
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  • 26
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    Hydrobiologia 230 (1992), S. 193-200 
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; ricefield system ; drainage channels ; mediterranean Deltas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen and phosphorus released into the water of a main drainage channel in the Ebro Delta was measured during a period of rice cultivation. An increase in total nitrogen and phosphorus in its different forms in accordance with the increase in cultivated area drained was observed. A significant correlation between the release of nutrients into the water and the nutrient load, for both nitrogen and phosphorus, if we consider the release of nutrients per unit of length of the channel and increased total phosphorus content of the water that flows through it during the period of rice cultivation. Physical and chemical changes in the water as a result of ricefield metabolism may explain the differences observed in nitrogen and phosphorus cycles between Ebro and Rhône Deltas, two mediterranean deltaic systems where a large area with similar drainage system is used for rice cultivation.
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  • 27
    ISSN: 1573-5117
    Keywords: nutrient regeneration ; phosphorus ; nitrogen ; sediment ; lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mineralization of phosphorus and nitrogen from seston was studied in consolidated sediment from the shallow Lake Arreskov (July and November) and in suspensions without sediment (July). In the suspension experiment, phosphorus and nitrogen were mineralized in the same proportions as they occurred in the seston. During the 30 days suspension experiment, 47 and 43% of the particulate phosphorus and nitrogen, respectively, was mineralized with constant rates. Addition of seston to the sediment had an immediate enhancing effect on oxygen uptake, phosphate and ammonia release, whereas nitrate release decreased due to denitrification. The enhanced rates lasted for 2–5 weeks, while the decrease in nitrate release persisted throughout the experiment. The increase in oxygen uptake (equivalent to 21% of the seston carbon) was, however, only observed in the July experiment. The release of phosphorus and nitrogen from seston decomposing on the sediment surface differed from the suspension experiments. Thus, between 91 and 111% of the phosphorus in the seston was released during the experiments. Due to opposite directed effects on ammonium and nitrate release, the resulting net release of nitrogen was relatively low. A comparison of C/N/P ratios in seston, sediment and flux rates indicated that nitrogen was mineralized faster than phosphorus and carbon. Some of this nitrogen was lost through denitrification and therefore not measurable in the flux of inorganic nitrogen ions. This investigation also suggests that decomposition of newly settled organic matter in sediments have indirect effects on sediment-water exchanges (e.g. by changing of redox potentials and stimulation of denitrification) that modifies the release of mineralized phosphate and nitrogen from the sediment.
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  • 28
    ISSN: 1573-5117
    Keywords: eutrophication ; lake restoration ; flushing ; Veluwemeer ; algal species ; transparency ; phosphorus ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Total phosphorus and chlorophyll decreased significantly after reduction of the external phosphorus loading and the start of flushing Veluwemeer with polder water in 1979. Flushing of Veluwemeer has had a large impact on nutrient dynamics. Especially in the first winter, dilution was the main cause of changes in water quality. On a longer term the increase of the inactivation of phosphorus in sediments is important. Oscillatoria agardhii has been brought to the margins of its habitat. Three successive cold winters were an additional causal factor in the disappearance of Oscillatoria agardhii and the dominance of diatoms and green algae from 1985 onwards. Due to higher detritus and inorganic suspended matter concentrations transparency increased less than expected. Since 1985 chlorophyll only contributes for a small percentage to the transparency. In the present situation further improvement of the water quality of Veluwemeer is questionable, as the phosphorus concentration in the lake and the polder water is almost the same. Therefore it is recommanded to shift flushing operations, at least in the winter period, from Veluwemeer towards Wolderwijd.
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  • 29
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    Hydrobiologia 238 (1992), S. 37-52 
    ISSN: 1573-5117
    Keywords: ammonium ; cyanobacteria ; diel ; diurnal ; mixing ; nitrate ; nitrogen ; periodicity ; phytoplankton ; protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transport and assimilation of the various forms of biologically available nitrogen by phytoplankton, and the subsequent biosynthesis of N-containing macromolecules, have the potential to respond in different ways during the daily growth cycle. This review examines five types of effect that may influence the daily pattern of nitrogen uptake and metabolism: light versus dark (the day/night cycle); changes in irradiance during the day (including the diurnal rise and fall in photon fluence rates); circadian rhythms (endogenous patterns of variation which may continue in the absence of external environmental forcing); periodic variations in exogenous nitrogen supply; and the 24-hour dynamics of stratification and mixing. The hydrodynamic effects operate through a variety of direct and indirect controls, and can substantially modify the diel rhythmicity of phytoplankton growth.
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  • 30
    ISSN: 1573-5117
    Keywords: fertilization ; phosphorus ; nitrogen ; phytoplankton ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Hecklan, in central Sweden, was fertilized with phosphorus and nitrogen during thermal stratification (late May-early Oct) 1984–1987. The nutrient additions were relatively small and raised the total phosphorus concentrations from 6 to 10 µg l−1. The working hypothesis was that this moderate increase in the phosphorus concentration could increase the phytoplankton biomass without adverse changes in the planktonic community structure. The fertilization increased the phytoplankton biomass from 0.1 to a maximum of 2 mm3 l−1. Chrysophyceae and Cryptophyceae dominated throughout the experimental period. Thus, the phytoplankton composition remained typical for a Swedish forest lake and provided a potential for increased zooplankton growth. An increased growth of zooplankton was indicated by increased biomass of Cladocera and Copepoda in 1984 and 1985, and by increased fecundity of herbivorous zooplankton.
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  • 31
    ISSN: 1573-515X
    Keywords: N2O ; CH4 ; red spruce ; balsam fir ; spruce-fir ; forests ; nitrogen ; deposition ; nitrification ; mineralization ; denitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured the exchange of N2O and CH4 between the atmosphere and soils in 5 spruce-fir stands located along a transect from New York to Maine. Nitrous oxide emissions averaged over the 1990 growing season (May–September) ranged from 2.1 ug N2O-N/m2-hr in New York to 0.4 ug N2O-N/m2-hr in Maine. The westernmost sites, Whiteface Mtn., New York and Mt. Mansfield, Vermont, had the highest nitrogen-deposition, net nitrification and N2O emissions. Soils at all sites were net sinks for atmospheric CH4 Methane uptake averaged over the 1990 growing season ranged from 0.02 mg CH4-C/M2-hr in Maine to 0.05 mg CH4-C/m2-hr in Vermont. Regional differences in CH4 uptake could not be explained by differences in nitrogen-deposition, soil nitrogen dynamics, soil moisture or soil temperature. We estimate that soils in spruce-fir forests at our study sites released ca. 0.02 to 0.08 kg N2O-N/ha and consumed ca. 0.74 to 1.85 kg CH4 C/ha in the 1990 growing season.
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  • 32
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    Biogeochemistry 15 (1992), S. 213-228 
    ISSN: 1573-515X
    Keywords: immobilization ; leaf litter decomposition ; lignin ; Mediterranean ecosystem ; nitrogen ; tannin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen immobilization in relation to the dynamics of lignin and tannins in nine different types of leaf litter was investigated during a 2-yr study at two Mediterranean ecosystems of SW Spain. Net nitrogen immobilization for all the species was higher in a forest than in the more nutrient-poor soil of a shrubland. Absolute amount of lignin increased in both ecosystems in the first 2–4 months whereas tannin rapidly decreased in the same time period. Increases in lignin were significantly correlated to losses of tannins during decomposition. Initial tannin content was the best predictor of the maximum amount of immobilized nitrogen in litter in both ecosystems. Mechanisms that could explain the immobilization of nitrogen in litter are discussed.
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  • 33
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    Biogeochemistry 18 (1992), S. 19-35 
    ISSN: 1573-515X
    Keywords: Dinitrogen fixation ; nitrogen ; phosphorus ; competition ; legumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An analysis of data compiled from the literature confirms a strong inverse relationship between annual rates of nitrogen fixation and the soil nitrogen content in agricultural and pastoral ecosystems. However, this inverse relationship is strongly modified by the rate of application of phosphorus fertilizer, which strongly influences the activities of both symbiotic and non-symbiotic nitrogen fixing organisms. In the case of symbiotic legumes, the response of N-fixation to N and P is in part a result of changes in legume dominance within the plant community. These results, as well as supporting data presented from a review of experiments on nitrogen fixation in a variety of other terrestrial and aquatic ecosystems, provide important support for the hypothesis that phosphorus availability is a key regulator of nitrogen biogeochemistry.
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  • 34
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    Biogeochemistry 18 (1992), S. 1-17 
    ISSN: 1573-515X
    Keywords: microbial biomass-N ; desert ; carbon ; nitrogen ; shrubland ; grassland ; playa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Microbial biomass nitrogen was measured in unamended (dry) and wetted soils in ten shrubland and grassland communities of the Chihuahuan desert, southern New Mexico, by the fumigation-extraction method. Microbial biomass-N in dry soils was undetectable. Average microbial biomass-N in wetted soils among all plant communities was 15.3 μg g-1 soil. Highest values were found in the communities with the lowest topographic positions, and the minimum values were detected in the spaces between shrubs. Microbial biomass was positively and significantly correlated to soil organic carbon and extractable nitrogen (NH4 + + NO3 -). In a stepwise multiple regression, organic carbon and extractable nitrogen accounted for 40.9 and 5.6%, respectively, of the variance in microbial biomass-N among all the samples. Among communities, the soil microbial biomass was affected by the ratio of carbon to extractable nitrogen. Our results suggest a succession in the control of microbial biomass from nitrogen to carbon when the ratio of carbon to nitrogen decreases during desertification.
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  • 35
    ISSN: 1573-515X
    Keywords: nitrogen ; phosphorus ; soil fertility ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured concentrations of soil nutrients (0–15 and 30–35 cm depths) before and after the dry season in control and dry-season irrigated plots of mature tropical moist forest on Barro Colorado Island (BCI) in central Panama to determine how soil moisture affects availability of plant nutrients. Dry-season irrigation (January through April in 1986, 1987, and 1988) enhanced gravimetric soil water contents to wet-season levels (ca. 400 g kg−1 but did not cause leaching beyond 0.8 m depth in the soil. Irrigation increased concentrations of exchangeable base cations (Ca2+, Mg2+, K+, Na+), but it had little effect on concentrations of inorganic N (NH4 +C, NO3 − and S (SO4 2−). These BCI soils had particularly low concentrations of extractable P especially at the end of the dry season in April, and concentrations increased in response to irrigation and the onset of the rainy season. We also measured the response of soil processes (nitrification and S mineralization) to irrigation and found that they responded positively to increased soil moisture in laboratory incubations, but irrigation had little effect on rates in the field. Other processes (plant uptake, soil organic matter dynamics) must compensate in the field and keep soil nutrient concentrations at relatively low levels.
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  • 36
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    World journal of microbiology and biotechnology 8 (1992), S. 579-584 
    ISSN: 1573-0972
    Keywords: Azolla ; fertilization ; nitrogen ; phosphate ; rice ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Rice performance, in terms of plant height, productive tillering, yield and N-contents of grain and straw, harvest index (grain yield as a percentage of grain plus straw yields) and relative fertilizer N-use efficiency (kg grain yield/kg fertilizer-N) was enhanced by urea, ZnSO4 and green manuring withAzolla caroliniana. Unlike urea fertilizer, calcium superphosphate increased the rate of azolla field colonization and promoted a thick, healthy dark-green mat of the fern. Response to ZnSO4 was higher in the azolla-free sub-subplots. Application of ZnSO4 corrected symptoms of Zn deficiency in rice but the addition of calcium superphosphate in the absence of Zn intensified the symptoms of Zn deficiency.
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  • 37
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    Journal of chemical ecology 18 (1992), S. 985-995 
    ISSN: 1573-1561
    Keywords: Plantago lanceolata ; iridoid glycosides ; aucubin ; catalpol ; nitrogen ; plant size ; plant-insect interactions ; chemical variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Variation in concentrations of leaf nitrogen and iridoid glycosides was examined in replicate plants of five genotypes ofPlantago lanceolata (Plantaginaceae) grown in an experimental garden. Nitrogen concentration and iridoid glycoside concentration were affected by leaf age. New leaves had nitrogen concentrations 1.7 to 2.7 times higher than mature leaves. Catalpol concentration was highest in new and intermediate-aged leaves. The concentration of aucubin, the biosynthetic precursor to catalpol, was higher in intermediate-aged leaves than in mature leaves, in three of five genotypes. Consequently, the proportion of aucubin relative to total iridoid glycosides increased as leaves aged. Concentration of iridoid glycosides was not correlated with plant size. Plant genotype significantly affected concentration of nitrogen and iridoid glycosides, as well as plant size. Thus, major indicators of hostplant quality for insect herbivores varied considerably both within and among plant genotypes and individuals.
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  • 38
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    Nutrient cycling in agroecosystems 31 (1992), S. 5-8 
    ISSN: 1573-0867
    Keywords: Water use- efficiency ; nitrogen ; nitrogen fertilization ; Triticum aestivum L. ; water-nitrogen interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract For 2 years, field experiments were conducted to study the direct and interactive effects of water and nitrogen uptake at different growth stages on grain yield of wheat, grown on coarse textured alluvial soil of Ludhiana. Twelve treatments comprising 3 irrigation regimes and 4 rates of N were imposed. The N and irrigation regimes showed significant interaction, especially during the drier year. Grain yield was better explained with water uptake and N uptake, when partitioned over different growth stages than with total uptake. The sensitivity factor for water uptake was higher at the reproductive stage (λ = 1.60) than at the vegetative (λ = 1.05) and maturation (λ = 0.38) stages. Contrary, yield was more sensitive to N uptake during the vegetative stage than the reproductive and the maturation stages. Sensitivity of grain yield to water uptake was higher at higher N application rates. Yield predictability was much better (R2 = 0.98) when N and water uptake at different growth stages were combined.
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  • 39
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    Nutrient cycling in agroecosystems 31 (1992), S. 15-19 
    ISSN: 1573-0867
    Keywords: Tillage ; crop rotation ; cereal grain ; wheat ; nitrogen ; sulfur ; phosphorus ; no-till
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efficient fertilizer use is a prerequisite for achieving optimum crop yield while avoiding environmental contamination. Cereal response to nitrogen (N), sulfur (S), and phosphorus (P) were determined for 6 years under differing tillage [conventional-till (CT) vs. no-till (NT)] and intensity of cropping (cereal/fallow vs. cereal/cereal). Semidwarf white winter wheat (Triticum aestivum L.) alternated yearly with either fallow or spring cereal [barley (Hordeum vulgare L.) or spring wheat] on a Typic Haploxeroll soil in a 415 mm rainfall zone. Fertilizer treatments were no fertilizer (None), N only (N), N plus S (NS), and N plus S plus P (NSP). Average application rate, when applied, was 109 kg N, 18 kg S, and 11 kg P ha−1. Average cereal yield without fertilizer was 1.82 t ha−1. Nitrogen increased grain yield in 6 of 6, S in 4 of 6, and P in 3 of 6 years, with P and S response significant the remaining years at the 10% probability level. Average yield increases were 1.11 t ha−1 for N, 0.93 t ha−1 for S, and 0.47 t ha−1 for P. The NT/CT yield ratio was 0.60, 0.75, 0.93, and 0.95 with None, N, NS, and NSP addition, respectively, indicating that N and S deficiency were more severe in no-till. Limited increase in the NT/CT ratio with P addition indicated that P deficiency was less affected by tillage. Winter wheat always yielded less under NT than CT regardless of fertility, whereas spring cereals reached equality when fertilized with NSP. Annually-cropped wheat yielded 52, 67, 89, and 90% of wheat after fallow with None, N, NS, and NSP, respectively. Thus N and S, but not P, deficiency was more intense with increased frequency of cropping. Adequate fertility was a prime prerequisite for efficient yield in all systems.
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  • 40
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    Nutrient cycling in agroecosystems 31 (1992), S. 35-41 
    ISSN: 1573-0867
    Keywords: Manganese ; nitrogen ; wheat ; Triticum aestivum L. ; take-all (Gaeumannomyces graminis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Five field experiments are described which measured the effect of take-all on grain yield of wheat when 5 levels of manganese fertilizer were applied in a factorial combination with 5 different types of nitrogen fertilizer. Ammonium nitrogen fertilizer, either as ammonium sulphate or ammonium chloride, lowered the severity of take-all. By contrast, sodium nitrate had no effect on the incidence and severity of take-all. Ammonium chloride and ammonium sulphate were equally effective at controlling take-all, suggesting that the chloride or sulphate ion had little or no effect on the disease. Manganese sulphate decreased take-all severity at two trial sites. Where manganese was deficient, an application of manganese lowered the severity of take-all, had no effect on the incidence and increased the dry matter and grain yields of the wheat plants. There were no beneficial effects of applied manganese if the wheat plants were adequately supplied with soil manganese. The results suggest that take-all is more severe where plants are deficient in either manganese or nitrogen. The work also suggests that manganese deficiency is not necessarily the reason why the wheat plants grown on the acid soils of south-west Western Australia are prone to take-all.
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  • 41
    ISSN: 1573-0867
    Keywords: Cultivation ; leaching ; mineralization ; mixed cropping ; nitrate ; nitrogen ; pasture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment was conducted to investigate the effect of timing and method of cultivation of a 3-year old ryegrass/white clover pasture on subsequent N mineralization, NO 3 - -N leaching, and growth and N uptake of a wheat crop in the following season. The size of various N pools and decomposition of14C-labelled ryegrass material were also investigated. Cultivation method (mouldboard or chisel ploughing) generally had no significant effect on the accumulation of mineral N in the profile in the autumn or on the amount of NO 3 - -N leached over winter.14C measurements suggested that initial decomposition rate of plant material was faster from May than March cultivation treatments. Despite this, overall net mineralization of organic N (of soil plus plant origin) increased with increasing fallow period between cultivation and leaching. The total amounts of mineral N accumulated in the soil profile before the start of leaching were 139, 119 and 22 kg N ha−1 for the March, May and July cultivated soils respectively. Cumulative leaching losses over the trial calculated from soil solution samples were 78, 40 and 5 kg N ha−1 for the March, May and July cultivated soils respectively. Differences in N mineralization over the season were generally not reflected by changes in amounts of potentially-mineralizable soil N (as measured by extraction or laboratory incubation) or levels of microbial biomass during the season. The amount of mineral N in the profile in spring increased with decreasing fallow period. This was reflected in an approximately 15% and 25% greater grain yield and N uptake respectively by the following wheat crop in plots cultivated in July rather than in March.
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  • 42
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    Nutrient cycling in agroecosystems 33 (1992), S. 107-114 
    ISSN: 1573-0867
    Keywords: Deep placement ; fertilizer efficiency ; injection ; nitrogen ; Oryza sativa L. ; pay-back period ; point placement ; urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To increase the fertilizer-N efficiency in lowland rice (Oryza sativa L.) cultivation, new management practices are needed. Main cause of the present low efficiency is the low N recovery by plants, as a considerable part of the N applied is lost; deep placement techniques improve the recovery. A pneumatic injector, with which urea prills can be point-placed at a depth of 5–10 cm in paddy soils, was tested in 38 on-farm trials in 1989/90, mostly during the wet season. The experiments, located in Africa and Asia, focussed on differences in grain yield between conventional methods of broadcasting urea and injection by the pneumatic injector, at recommended N-rates. The study shows that the pneumatic injector is effective as a tool to improve the N fertilizer efficiency. The average yield increases per region, resulting from the use of the injector, ranged from about 250 to 1300 kg grain ha−1. The value of the yield increase would allow most farmers to recover the costs of the injector within one season, even if labour was hired to carry out the injections. The average labour requirement of the injector was 40 hours ha−1. In Indonesia, injection of prilled urea gave yields similar to those obtained with urea briquettes.
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  • 43
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    Nutrient cycling in agroecosystems 33 (1992), S. 257-265 
    ISSN: 1573-0867
    Keywords: ammonia volatilization ; faeces ; grazed swards ; nitrogen ; urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The micrometeorological mass balance method was used to measure ammonia (NH3) volatilization from rotationally grazed swards throughout the 1987 and 1988 growing seasons. In both years the swards were dressed with calcium ammonium nitrate (CAN) split over 7 dressings. In 1987 the sward received a total of 550 kg N ha−1, in 1988 a total of 550 or 250 kg N ha−1. For the 550 kg N ha−1 treatments there were 8 and 9 grazing cycles, respectively, in 1987 and 1988 and 7 for the 250 kg N ha−1 treatment. Losses from the 550 N sward were 42.2 and 39.2 kg N ha−1 in 1987 and 1988, respectively; this was equivalent to 8.5 and 7.7% of the N returned to the sward in the excreta of the grazing cattle. The NH3 loss from the 250N sward was 8.1 kg N ha−1 in 1988, which was equivalent to 3.1% of the N returned to the sward in excreta during the growing season. There was a wide variation in NH3 volatilization between the individual grazing periods. This indicates the necessity of continued measurements throughout the growing season to obtain reliable data on NH3 volatilization. Soil humidity is suggested to be a key factor, because emissions were high from wet soil, and low from drier soil. Results of a Monte Carlo simulation study showed that the measured NH3 loss from the 250 and 550 N swards had a standard deviation of 13 and 5% of the mean, respectively.
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  • 44
    ISSN: 1572-9729
    Keywords: calcium ; fine roots ; nitrogen ; northern hardwood ; nutrient dynamics ; seasonality ; soils ; sulfur ; vegetation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seasonal dynamics of S, Ca and N were examined at the Huntington Forest, a northern hardwood ecosystem in the central Adirondacks of New York for a period of 34 months (1985–1988). Solute concentrations and fluxes in bulk precipitation, throughfall (TF) and leachates from the forest floor, E horizon and B horizon were quantified. Both above and below-ground elemental fluxes mediated by vegetation (e.g. uptake, litter inputs, and fine roots production) were also determined. The roles of abiotic and biotic processes were ascertained based on both changes in solute concentrations through the strata of the ecosystem as well as differences between dormant and growing seasons. Concentrations of SO4 2−, NO3 −, NH4 + and Ca2+ were greater in TF than precipitation. Forest floor leachates had greater concentrations of SO4 2−, NO3 − + NH4 + and Ca2+ (9, 6 and 77 µeq L−1, respectively) than TF. There were differences in concentrations of ions in leachates from the forest floor between the dormant and growing seasons presumably due to vegetation uptake and microbial immobilization. Concentrations and fluxes of NO3 − and NH; were greatest in early spring followed by a rapid decline which coincided with a demand for N by vegetation in late spring. Vegetation uptake (44.7 kg N ha−1 yr−1 ) could account for the low leaching rates of N03 −. Within the mineral soil, changes with soil depth and the absence of seasonal patterns suggest that cation exchange (Ca+) or anion sorption (SO4 2−) are primarily responsible for regulating solute concentrations. The increase in SO4 2− concentration after leachates passed through the mineral soil may be attributed to desorption of sulfate that was adsorbed during an earlier period when SO4 2− concentrations would have been greater due to elevated S inputs.
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  • 45
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; underwater light ; primary production ; secondary production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The study provides a 2.5 year record of Rhenosterkop Dam (KwaNdebele, South Africa) plankton population dynamics and production in relation to physical and chemical changes which occurred during the trophic depression and stabilization phases of the reservoir. The mean volume of the reservoir was 4% of full storage capacity. Water temperatures ranged from 14 °C to 27 °C. Due to inorganic suspensoids, the euphotic zone averaged 2.6 m. An anaerobic zone developed each summer. The nitrogen, soluble reactive phosphorus (SRP) and silica concentrations did not displaya seasonal pattern, but the latter two nutrients declined over the study. The dominant phytoplankton group was the cryptophytes while the zooplankton population was dominated by crustaceans. Chlorophyll a concentrations ranged from 1.1 to 27 mg m−3 and were positively correlated to silica and SRP concentrations and inversely with NH4-N concentrations. Primary production ranged from 22.6 to 375 mgC m−2 h−1; changes in Amax were positively correlated to silica and SRP concentrations. Total zooplankton dry weight biomass varied from 〈0.5 to 〉4 mg l−1. Annual zooplankton (secondary) production was 8 to ∼ 15 gC m−3 a−1; both primary and secondary production were greatest in the first 12 months of study and remained at low levels for the remainder, similar to the trends for silica and SRP. The data indicate that the reservoir shifted from eutrophic to mesotrophic during the study, typical of events in new reservoirs, and that changes in the plankton populations were largely the result of changing nutrient concentrations.
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  • 46
    ISSN: 1573-5036
    Keywords: bulk density ; epoxy resin impregnation ; image analysis ; macroporosity ; nitrogen ; stability ; strength ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil aggregate stability, organic matter content, pH, bulk density, strength, and macropore attributes were assessed in order to evaluate the influence of grass root growth in a field sward. The amount of grass grown was varied by varying the quantity of applied nitrogen fertilizer: following one year with a uniform application rate, nitrogen fertilizer was applied over the subsequent three years to a compact soil at zero (N0), moderate (N1) and high (N2) rates. Differences in herbage production were evident in the three years of the contrasting nitrogen treatments. An index of soil aggregate stability increased in response to the increased grass growth promoted by heavier applications of nitrogen, but both bulk density and vane shear strength were unchanged. Binary images of the soil solid and pore space showed that for each treatment the largest volume of macropores occurred close to the surface, particularly in N0 where there was more pore space than in either N1 or N2. Analysis of the pore structure attributes of the binary images revealed further differences between treatments, in particular, at 40–80 mm depth, the soil in treatment N0 had fewer and smaller pores, and greater distance between pores, than the soil in the N1 and N2 treatments. The larger macropore volume in N1 and N2 constituted a major portion of the air-filled porosity when the soil was relatively wet. It was concluded that the root growth in the intensively cropped grassland was conducive to maintenance of a relatively stable and porous soil structure. An attendant increase in soil acidity close to the soil surface was a disadvantage of the larger nitrogen inputs.
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  • 47
    ISSN: 1573-5036
    Keywords: carbohydrate translocation ; defoliation ; nitrogen ; white clover (Trifolium repens L.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Clonal plants of white clover (Trifolium repens L.) were grown in a controlled environment with either low or high rates of applied nitrate-N (providing, notionally, insufficient or sufficient N for unrestricted growth), or in the absence of applied N. Plants receiving no nitrate-N were inoculated with Rhizobia and fixed their own N2. All plants were maintained with a maximum of three fully unfolded leaves per apex (‘lenient defoliation’) until day 68 when half of the plants were severely defoliated. The export and translocation of carbohydrates from the first fully unfolded main stolon leaf was measured three days later using 14C. Reduced carbon translocation to stolon tissue and roots, and increased translocation to young branches, occurred following severe defoliation in all three nitrogen treatments. However, N-deficient plants showed large reductions in total export of carbohydrates (44 vs. 17% of 14C assimilated for lenient vs. severe defoliation) whereas N-sufficient plants (either receiving nitrate-N or fixing their own N2) showed small increases in total export (means of 54% vs. 62% in the respective defoliation treatments). Furthermore, carbohydrate translocation to old branches ceased altogether in severely defoliated, N-deficient plants, but increased in severely defoliated, N-sufficient plants, illustrating that plant responses to multiple-factor stresses may differ greatly from those seen as the result of single-factor stresses. Interactions between nitrogen nutrition and defoliation in total carbohydrate export, and in carbohydrate supply to old branches, could have serious negative effects on the short-term C economy and physiological integration, and hence on the adaptability, of clonal plants growing with a mineral deficiency in the presence of grazing animals.
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  • 48
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphorus ; root: shoot ratios ; secondary succession ; semiarid ; shrubland ; tissue nitrogen ; tissue phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Above- and below-ground biomass production, nitrogen (N) and phosphorus (P) tissue concentrations, and root: shoot ratios were examined for five species that are characteristic of a semiarid successional sequence under controlled greenhouse conditions. In two simultaneous experiments, seedlings of one forb, two grass, and two shrub species important in a sagebrush successional sere, were subjected to seven levels of N and P. Results of the experiments suggest distinct differences in nutrient response patterns between early and late seral species. Early seral species produced more biomass but had lower tissue nutrient concentrations than late seral species. As N and P availabilities decreased, late seral species displayed characteristics indicative of increasing competitive advantage over those of early seral species. Root: shoot ratios of the five species primarily reflected patterns related to lifeform, but with some early and late seral characteristics. Results from this study 1) confirm that nutrient use pattern, nutrient availability, and seral position relationships characteristic of mesic ecosystems hold equally true for semiarid systems, and 2) suggest that nutrients are important organizing factors in semiarid ecosystems.
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  • 49
    ISSN: 1573-515X
    Keywords: algae ; nitrogen ; nutrient ; phosphorus ; regeneration ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Most ecosystem models consolidate members of food-webs, e.g. species, into a small number of functional components. Each of these is then described by a single state variable such as biomass. When a multivariate approach incorporating multiple substances within components is substituted for this univariate one, a ‘stoichiometric’ model is formed. Here we show that the Nitrogen:Phosphorus ratio within zooplankton herbivores varies substantially intraspecifically but not intraspecifically. By using stoichiometric theory and recent measurements of the N:P ratio within different zooplankton taxa, we calculate large differences in ratios of nutrients recycled by different zooplankton species. Finally, we demonstrate that N:P stoichiometry can successfully account for shifts in N- and P-limitation previously observed in whole-lake experiments. Species stoichiometry merges food-web dynamics with biogeochemical cycles to yield new insights.
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  • 50
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    Wetlands ecology and management 1 (1992), S. 239-247 
    ISSN: 1572-9834
    Keywords: biomass ; carbohydrates ; nitrogen ; phosphorus ; Phragmites australis ; potassium ; reed ; rhizome ; translocation ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands. Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (〈 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m−2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June. Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (〉 1000 g m−2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites. The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that “reloading” of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management. Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves.
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  • 51
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    Journal of chemical ecology 18 (1992), S. 2095-2105 
    ISSN: 1573-1561
    Keywords: Allelopathy ; Schizachyrium scoparium ; Ceratiola ericoides ; hydrocinnamic acid ; nitrogen ; phosphorus ; potassium ; fire ; sand pine scrub ; sandhill
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Bare zones around shrubs in the Florida scrub indicate the possibility of allelopathy by shrubs controlling the distribution of grasses invading from adjacent sandhills. The allelochemical, hydrocinnamic acid, has been identified as a breakdown product of ceratiolin, which is released from the shrubCeratiola ericoides. Here, hydrocinnamic acid (HCA) was shown to have a strongly inhibitory effect on shoot and root biomass of the grassSchizachyrium scoparium in greenhouse bioassays lasting 4.5 months. Linear increases in the concentration of HCA from 0 to 200 ppm, applied biweekly, resulted in exponential decreases in root and shoot biomass at harvest. Plants grown at 200 ppm HCA had root and shoot biomasses 13% and 17% of controls, respectively. Concurrent investigation of reduced nutrient levels indicated greater inhibition by HCA in a reduced nitrogen (N) treatment and in a reduced potassium (K) treatment relative to HCA inhibition in the full nutrient treatment. The negative slopes of the regressions of log of biomass on HCA concentration were steepest in the reduced N and reduced K treatments. Root and shoot biomasses in reduced N treatments were 20–43% and 24–34% less than the respective biomasses in the full nutrient treatment. Comparable reductions in the reduced K treatment were as much as 19% and 10% for root and shoot biomasses, respectively. The effects of HCA in a reduced phosphorus (P) treatment and in a reduced P and K treatment were not significantly different from the effects of HCA in the full nutrient treatment. Extraction of the soils at harvest indicated no buildup of HCA at the end of the experiment. The sensitivity ofSchizachyrium scoparium to HCA in general and increased sensitivity under low N and low K solutions may be important in the Florida scrub community where levels of N and K are known to be low.
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  • 52
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    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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  • 53
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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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  • 54
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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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  • 55
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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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  • 56
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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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  • 57
    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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  • 58
    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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  • 59
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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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  • 60
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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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  • 61
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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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  • 62
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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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  • 63
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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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  • 64
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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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  • 65
    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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  • 66
    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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  • 67
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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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  • 68
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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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  • 69
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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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  • 70
    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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  • 71
    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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  • 73
    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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  • 74
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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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  • 75
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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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  • 76
    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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  • 79
    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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  • 81
    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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  • 82
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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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  • 83
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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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  • 84
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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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  • 85
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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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  • 86
    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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  • 87
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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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  • 88
    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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  • 89
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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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  • 90
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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
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    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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  • 91
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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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  • 92
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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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  • 93
    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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  • 94
    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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  • 95
    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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  • 96
    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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  • 97
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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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  • 98
    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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  • 99
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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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  • 100
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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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