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  • Articles  (212)
  • Nitrogen  (211)
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  • Chemical Engineering
  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (212)
  • 1
    Electronic Resource
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    Springer
    Biology and fertility of soils 31 (2000), S. 470-477 
    ISSN: 1432-0789
    Keywords: Key words Cover crop ; Nitrogen ; Corn ; Available N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  This study was conducted to determine effects of long-term winter cover cropping with hairy vetch, cereal rye and annual ryegrass on soil N availability and corn productivity. From 1987 to 1995, with the exception of the first year of the study, the cover crops were seeded each year in late September or early October after the corn harvest and incorporated into the soil in late April or early May. Corn was seeded 10 days to 2 weeks after the cover crop residues had been incorporated, and N fertilizer was applied as a side-dressing at rates of 0, 67, 134, or 201 kg N ha–1 each year. While the average annual total N input from the above-ground biomass of the cover crops was highest for hairy vetch (72.4 kg N ha–1), the average annual total C input was highest for cereal rye (1043 kg C ha–1) compared with the other cover crops. Hairy vetch was the only cover crop that significantly increased pre-side-dressed NO3 –-N (Ni) corn biomass and N uptake at 0 N. At an N fertilizer rate of 134 kg N ha–1 or higher, the cover crops had a minimal effect on corn biomass. This indicated that even after 9 years of winter cover cropping, the effect of the cover crops on corn growth resulted primarily from their influence on soil N availability. The amount of available N estimated from the cover crops (Nac) was significantly correlated with relative corn biomass production (r 2=0.707, P〈0.001). The total amount of available N, comprising Nac and N added from fertilizer (Nf), was strongly correlated (r 2=0.820, P〈0.001)) with relative corn biomass production. The correlation was also high for the available N comprising Ni and Nf (r 2=0.775, P〈0.001). Although cereal rye and annual ryegrass did not improve corn biomass production in the short term, they benefited soil organic N accumulation and gradually improved corn biomass production compared with the control over the long term.
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  • 2
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    Sciences of soils 5 (2000), S. 10-21 
    ISSN: 1432-9492
    Keywords: Soil temperature ; Triticum aestivum ; Stubble retention ; Nitrogen ; Early growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Early growth and development are often lower when wheat is sown into standing stubble. A study was conducted to determine whether this difference in early growth could be explained by the effects of stubble on soil temperature in the vicinity of the young plant. The roles of nitrogen nutrition and soil strength were also assessed. Three crops were monitored (1990–1992), with the wheat being sown into either standing wheat stubble after a no-till fallow (NT), or into no-tilled plots from which the stubble had been removed by burning (NB). Measurements were made of wheat growth and development, soil and plant N, soil temperature and penetration resistance. The site was on a black earth near Warialda in the northern wheatbelt of New South Wales, Australia. In 1992 wheat was also grown under simulated stubble to isolate the shading and soil temperature effects of stubble from other factors. A significant (P〈0.05) relationship was found between average soil temperature and above ground dry matter (DM) at 65 days after sowing (DAS) but not at 107 DAS. This relationship accounted for differences in DM production at 65 DAS between NT and NB treatments in 1991 and 1992, but not in 1990. In that year the lower DM production in NT plots was associated with poorer N nutrition, and possibly disease. Laboratory incubations indicate that immobilisation of N as stubble decomposed could have contributed to this. Burning stubble produced no immediate increase in soil N availability, so that it is unlikely that N contained in stubble contributed to the difference. Soil strength differences between treatments and phytotoxic effects are unlikely to have contributed to growth differences in this soil.
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  • 3
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    Biology and fertility of soils 28 (1999), S. 204-211 
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Balances between nutrients applied or mineralized and nutrients removed in maize grain and stover were calculated in a hedgerow intercropping experiment in which Leucaena leucocephala and L. pallida prunings and cattle manure were applied. Hedgerow intercropping (also called alley cropping) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. In control treatments, nutrient depletion per season was in the order of 7–19 kg N ha–1, 4–12 kg P ha–1, 10–26 kg K ha–1, 0–2 kg Ca ha–1 and 3–6 kg Mg ha–1. N fertilizer reversed the depletion of N, but it accelerated the depletion of the other nutrients. Manure and at least two applications of leucaena prunings resulted in net positive balances of N, K, and Ca between amounts applied or mineralized and amounts removed by maize. The amounts of P and Mg applied with, or mineralized from, prunings or manure were insufficient to offset the negative balances of these nutrients.
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  • 4
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    Biology and fertility of soils 29 (1999), S. 38-45 
    ISSN: 1432-0789
    Keywords: Key words Grassland ; Nitrogen ; Mineralization ; Macro-organic matter ; Soil particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  A study was conducted to determine mineralization rates in the field and in different soil layers under three grassland managements (viz. a reseeded sward, a permanent sward with a conventional N management, and a long-term grass sward with 0 N (0-N) input). Potential mineralization rates of soil particles (sand, silt and clay) and macro-organic matter fractions of different sizes (i.e. 0.2–0.5, 0.5–2.0 and 〉2 mm) were also determined in the laboratory. In the reseeded plots, net mineralization was unchanged down to 40 cm depth. In the undisturbed conventional-N swards, mineralization rates were substantially higher in the top layer (0–10 cm) than in the deeper layers. In plots which had received no fertilizer N, mineralization was consistently low in all the layers. There was more macro-organic matter (MOM) in the 0-N plots (equivalent to 23 g kg–1 soil for 0–40 cm) than in the two fertilized plots (i.e. conventional-N and reseeded) which contained similar amounts (ca. 15 g kg–1 soil). C and N contents of separated soil particles did not differ amongst the treatments, but there were large differences with depth. Potential mineralization in the bulk soil was greatest in the 0–10 cm layers and gradually decreased with depth in all the treatments. Separated sand particles had negligible rates of potential mineralization and the clay component had the highest rates in the subsurface layers (10–40 cm). MOMs had high potential rate of mineralization in the surface layer and decreased with soil depth, but there was no clear pattern in the differences between different size fractions.
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  • 5
    ISSN: 0931-1890
    Keywords: Key words Picea abies ; Photosynthesis ; Nitrogen ; Temperature ; Shoot growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Branches of 30-year-old Norway spruce [Picea abies (L.) Karst.] trees were enclosed in ventilated, transparent plastic bags and flushed with air containing ambient (A≈370 μmol CO2 mol–1) or ambient plus 340 μmol CO2 mol–1 (EL). Light-saturated photosynthesis was on average 56% higher in EL compared to A. Branch phenology and morphology were strongly related to nitrogen concentration (mg g–1 dry mass) in the foliage and to elevated temperatures in the bags, but no direct effect of EL was found. In 1995, budbreak occurred on average 4 days earlier in the bags compared to the control branches, which was partly explained by the temperature elevation in the bags. No nutrient or EL effect on budbreak was found. Increases in temperature and nitrogen supply increased shoot growth: together they explained 76% of the variation in the extension rate, 63% of the variation in extension duration and 65% of the variation in final length of leading shoots. Shoot morphology was altered both by increased nitrogen availability and by the enclosure induced environmental changes inside the bags, leading to reduced mutual shading between needles. Specific needle area (SNA) was lower in EL, but this was related to lower nitrogen concentrations. Total dry mass of the branches was unaffected by EL. It is concluded that treating individual branches of Norway spruce with elevated CO2 does not increase branch growth. The nutrient status of the branch and climate determine its growth, i.e. its sink strength for carbon. Increased export of carbohydrates to the rest of the tree is probable in EL treated branches.
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  • 6
    ISSN: 1432-0789
    Keywords: Key words Grasslands ; Management ; Microbial biomass ; Bacteria ; Fungi ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  There is much interest in the development of agricultural land management strategies aimed at enhancing reliance on ecosystem self-regulation rather than on artificial inputs such as fertilisers and pesticides. This study tested the usefulness of measures of soil microbial biomass and fungal:bacterial biomass ratios as indicators of effective conversion from an intensive grassland system, reliant mainly on fertilisers for crop nutrition, to a low-input system reliant mainly on self-regulation through soil biological pathways of nutrient turnover. Analysis of soils from a wide range of meadow grassland sites in northern England, along a gradient of long-term management intensity, showed that fungal:bacterial biomass ratios (measured by phospholipid fatty acid analysis; PLFA) were consistently and significantly higher in the unfertilised than the fertilised grasslands. There was also some evidence that microbial biomass, measured by chloroform fumigation and total PLFA, was higher in the unfertilised than in the fertilised grasslands. It was also found that levels of inorganic nitrogen (N), in particular nitrate-N, were significantly higher in the fertilised than in the unfertilised grasslands. However, microbial activity, measured as basal respiration, did not differ between the sites. A field manipulation trial was conducted to determine whether the reinstatement of traditional management on an improved mesotrophic grassland, for 6 years, resulted in similar changes in the soil microbial community. It was found that neither the cessation of fertiliser applications nor changes in cutting and grazing management significantly affected soil microbial biomass or the fungal:bacterial biomass ratio. It is suggested that the lack of effects on the soil microbial community may be related to high residual fertility caused by retention of fertiliser N in the soil. On the basis of these results it is recommended that following the reinstatement of low-input management, the measurement of a significant increase in the soil fungal:bacterial biomass ratio, and perhaps total microbial biomass, may be an indicator of successful conversion to a grassland system reliant of self-regulation.
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  • 7
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    Biology and fertility of soils 29 (1999), S. 430-433 
    ISSN: 1432-0789
    Keywords: Key words Carbon ; Nitrogen ; Microbial biomass ; Mineralization ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of acetate additions to northern hardwood forest soils on microbial biomass carbon (C) and nitrogen (N) content, soil inorganic N levels, respirable C and potential net N mineralization and nitrification were evaluated. The experiment was relevant to a potential watershed-scale calcium (Ca) addition that aims to replace Ca depleted by long-term exposure to acid rain. One option for this addition is to use calcium-magnesium (Mg) acetate, a compound that is inexpensive and much more readily soluble than the Ca carbonate that is generally used for large-scale liming. Field plots were treated with sodium (NA) acetate, Na bicarbonate or water (control) and were sampled (forest floor – Oe and Oa combined) 2, 10 and 58 days following application. It was expected that the addition of C would lead to an increase in biomass C and N and a decrease in inorganic N. Instead, we observed no effect on biomass C, a decline in biomass N and an increase in N availability. One possible explanation for our surprising results is that the C addition stimulated microbial activity but not growth. A second, and more likely, explanation for our results is that the C addition did stimulate microbial growth and activity, but there was no increase in microbial biomass due to predation of the new biomass by soil fauna. The results confirm the emerging realization that the effects of increases in the flow of C to soils, either by deliberate addition or from changes in atmospheric CO2, are more complex than would be expected from a simple C : N ratio analysis. Evaluations of large-scale manipulations of forest soils to ameliorate effects of atmospheric deposition or to dispose of wastes should consider microbial and faunal dynamics in considerable detail.
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  • 8
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    Biology and fertility of soils 28 (1999), S. 182-195 
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus ; Intercropping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  A litter bag technique was used to study the decomposition and release of N, P, K, Ca, and Mg from Leucaena leucocephala and L. pallida prunings and cattle manure in a hedgerow intercropping trial conducted in the Ethiopian highlands. Hedgerow intercropping (also called alley cropping or alley farming) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. Manure was the most resistant to decomposition, losing only 15% of its dry matter (DM) in 15 weeks, compared to 41–57% lost by leucaena prunings. Large quantities of K (up to 104 kg ha–1) were mineralized from prunings and manure, but Ca and Mg were mostly immobilized. More N and P were released from prunings than from manure, which resulted in net immobilization of these nutrients in the initial stages of decomposition and net mineralization in later stages. Between the leucaenas more N was mineralized and less Ca and Mg were immobilized when L. leucocephala prunings were applied than when L. pallida prunings were applied. Fertilizer N increased DM decomposition and N mineralization. Mineralization of the nutrients was constrained by lignin and polyphenol contents. It is concluded that leucaena mulch and cattle manure may be significant sources of N and K for crop growth, but external sources of P, Ca and Mg may be required, particularly in acid soils which have low contents of these nutrients. However, this fertility effect has to be evaluated against the competition effect of trees to predict crop response.
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  • 9
    ISSN: 1432-0789
    Keywords: Key words Alley cropping ; Calcium ; Magnesium ; Nitrogen ; Phosphorus ; Leaf pruning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of Leucaena leucocephala and L. pallida prunings and cattle manure on maize nutrient uptake and yield were investigated in a hedgerow intercropping trial in the Ethiopian highlands. Hedgerow intercropping (also called alley cropping) is an agroforestry system in which trees are grown in dense hedges between alleys where short-cycle crops are grown. The hedges are pruned periodically during the cropping period and the prunings are added to the soil as green manure. For each leucaena species, the experiment had 16 treatments resulting from a factorial combination of four levels of leucaena leaf prunings (no prunings applied; first prunings applied; first and second prunings applied; first, second and third prunings applied), two levels of air-dried cattle manure (0 and 3 t dry matter ha–1) and two levels of N fertilizer (0 and 40 kg N ha–1 as urea). Uptake of N, P and K increased significantly with application of the three nutrient sources, but uptake of Ca and Mg either did not respond or decreased with application of prunings and manure. All the three factors increased maize grain and stover yields significantly, usually with no significant interactions between the factors. At least two applications of prunings were required to significantly increase nutrient uptake and maize yield. Maize in the row closest to the hedge did not respond to these nutrient inputs. It is concluded that hedgerow intercropping, with or without manure application, can increase crop yields moderately (to 2–3 t ha–1 maize grain yields) in the highlands, but P, Ca and Mg may have to be supplied from external sources if they are deficient in the soil. Additional N is still required for higher yields (〉4 t ha–1 maize grain yields). However, quantification of the competition effects of the trees is also required to confirm these results.
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  • 10
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    Plant and soil 216 (1999), S. 83-91 
    ISSN: 1573-5036
    Keywords: Cunninghamia lanceolata ; Fertilization ; Nutrient loading ; Nitrogen ; Retranslocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient loaded and non-loaded Chinese fir (Cunninghamia lanceolata (Lamb) Hook) seedlings were transplanted in a pot trial to examine effects of exponential nutrient loading and fertilization treatments on first season growth and N nutrition. The treatments tested four rates of N (0, 30, 60, and 90 mg tree-1) as a mixed NPK fertilizer applied before planting to create a soil fertility gradient, and two topdressings applied only to non-loaded seedlings later in the season. Nutrient loading alone consistently enhanced seedling growth on the four soil fertility classes, increasing respective biomass and N uptake 42, 45, 20 and 8%, and 65, 67, 29 and 18% more than non-loaded seedlings. The positive response was attributed to increased N retranslocation from higher nutrient reserves built up by loading during nursery culture. Net retranslocation from old shoots to new growth was highest soon after planting when nutrient stress was most severe. Pre-plant soil fertilization and post-plant topdressings were also effective in promoting seedling productivity, but equivalent additions yielded less biomass than that from nutrient loading alone. Implications are that exponential nutrient loading may be more efficient in improving early growth performance of Chinese fir seedlings than traditional field fertilization practices at plantation establishment, and may on competitive sites avoid problems of stimulating surrounding vegetation rather than trees.
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  • 11
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    Biology and fertility of soils 26 (1998), S. 313-322 
    ISSN: 1432-0789
    Keywords: Key words Fungi ; Bacteria ; Nitrogen ; Scots pine ; Stratification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The abundance and micro-stratification of bacteria and fungi inhabiting the organic layers of a Scots pine forest (Pinus sylvestris L.) were investigated. An experiment using stratified litterbags, containing organic material of four degradation stages (fresh litter, litter, fragmented litter and humus) was performed over a period of 2.5 years. Dynamics and stratification of fluorescent stained bacteria and fungi, ratios between bacterial and fungal biomass, and relationships with moisture and temperature are described. Average bacterial counts in litter and fragmented litter were similar, i.e., approximately 5×109 bacteriag–1 (dry weight) organic matter, and significantly exceeded those in humus. The mean bacterial biomass ranged from 0.338 to 0.252mg carbon (C) g–1 (dry weight) organic matter. Lengths of mycelia were significantly below the usually recorded amounts for comparable temperate coniferous forests. The highest average hyphal length, 53mg–1 (dry weight) organic matter, was recorded in litter and decreased significantly with depth. The corresponding mean fungal biomass ranged from 0.050 to 0.009mg Cg–1 (dry weight). The abundance of bacteria and fungi was influenced by water content, that of fungi also by temperature. A litterbag series with freshly fallen litter of standard quality, renewed bimonthly, revealed a clear seasonal pattern with microbial biomass peaks in winter. The mean hyphal length was 104mg–1 (dry weight) and mean number of bacteria, 2.40×109 bacteria g–1 (dry weight). Comparable bacterial and fungal biomass C were found in the freshly fallen litter [0.154 and 0.132mgCg–1 (dry weight) organic material, respectively]. The ratio of bacterial-to-fungal biomass C increased from 1.2 in fresh litter to 28.0 in humus. The results indicate the existence of an environmental stress factor affecting the abundance of fungi in the second phase of decomposition. High atmospheric nitrogen deposition is discussed as a prime factor to explain low fungal biomass and the relatively short lengths of fungal hyphae in some of the forest soil layers under study.
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  • 12
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    Biology and fertility of soils 27 (1998), S. 279-283 
    ISSN: 1432-0789
    Keywords: Key words Peats ; Methane ; Nitrogen ; Land use ; Agriculture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Rates of methane uptake were measured in incubation studies with intact cores from adjacent fenland peats that have been under arable management and woodland management for at least the past 30 years. On two separate occasions the woodland peat showed greater rates of uptake than the arable peat. These rates ranged from 23.1 to 223.3 μg CH4 m–2 day–1 for the woodland peat and from 29.6 to 157.6 μg CH4 m–2 day–1 for the arable peat. When the peats were artificially flooded there was a decrease in the rate of methane oxidation, but neither site showed any net efflux of methane. 15N isotopic dilution was used to characterise nitrogen cycling within the two peats. Both showed similar rates of gross nitrogen mineralisation (3.58 mg N kg–1 day–1, arable peat; 3.54 N kg–1 day–1, woodland peat) and ammonium consumption (4.19 arable peat and 4.70 mg N kg–1 day–1 woodland peat). There were significant differences in their inorganic ammonium and nitrate pool sizes, and the rate of gross nitrification was significantly higher in the woodland peat (4.90 mg N kg–1 day–1) compared to the arable peat (1.90 mg N kg–1 day–1). These results are discussed in the light of high atmospheric nitrogen deposition.
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  • 13
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    Biology and fertility of soils 28 (1998), S. 56-63 
    ISSN: 1432-0789
    Keywords: Key words Animal manure ; Immobilization ; Mineralization ; Nitrogen ; Slurry distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  An improved understanding of the cycling of animal manure N is a prerequisite for making better use of this N source. A sheep was fed 15N-labelled grass in order to study the fate of 15N-labelled ruminant manure N in the plant-soil system. The uniformity of labelling was found to be satisfactory when an appropriate feeding strategy was used. The mineralization of labelled faecal N was compared to the mineralization of labelled feed N and indigestible feed N by measuring residual labelled organic N in unplanted topsoil in the field. After 18 months, 61% of both faecal N and feed N was recovered in organic form in the topsoil, while 94% of the indigestible feed N was still present in the soil. The influence of slurry distribution in soil on the crop uptake of labelled faecal N in slurry was studied in a sandy and a sandy loam soil. The crop uptake of labelled faecal N was compared with the uptake of 15N-labelled mineral fertilizer in a reference treatment. The uptake was 28–32% of that of the reference treatment with simulated slurry injection, 13–25% with incorporated slurry and 18–19% with slurry on the soil surface. The mineralization of faecal N in the autumn after application in spring was low irrespective of the slurry distribution in soil. The results demonstrate that the contact between animal manure and the soil matrix significantly influences the short-term turnover and availability of faecal and ammonium N in slurry, especially in fine-textured soils.
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  • 14
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    Biology and fertility of soils 26 (1998), S. 258-267 
    ISSN: 1432-0789
    Keywords: Key words Decomposition ; Deposition ; Nitrogen ; saturation ; Pinus sylvestris ; Soil biota
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Wekerom forest shows a high nitrogen (N) load, and the first signs of N saturation. This characterization is based on the high N content of the needles, the high nitrate-N (NO3-N) mobilization and low cation mobilization from the organic horizon. The N cycle in this forest has been transformed into an „open flow” system, in which the ammonium-N, deposited in large quantities from the atmosphere, is transformed into NO3-N, which is leached into the groundwater. Decomposition of deeper organic layers, such as the fragmented litter and humus layers, is thought to provide additional NH4-N, which explains the high NO3-N output. Together with a reduction in the number and vitality of the pine trees, there is an increase in the number of nitrophilous plants, such as Deschampsia flexuosa and Rumex acetosella. The ectomycorrhizal and litter-decaying fungi are specific, N-resistant species. Soil fauna are classified as common inhabitants of dry, acid, nutrient poor forests.
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  • 15
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    Biology and fertility of soils 26 (1998), S. 243-249 
    ISSN: 1432-0789
    Keywords: Key words Earthworm middens ; Soil ; Carbon ; Nitrogen ; Microbial activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Earthworm activity may be an important cause of spatial and temporal heterogeneity of soil properties in agroecosystems. Structures known as “earthworm middens,” formed at the soil surface by the feeding and casting activities of some earthworms, may contribute significantly to this heterogeneity. We compared the temporal dynamics of carbon (C), nitrogen (N), and microbial acitivity in Lumbricus terrestris middens and in surrounding non-midden (bulk) soil during the spring, when seasonal earthworm activity was high. We sampled soil from middens and bulk soil in a no-till cornfield on four dates during May and June 1995. Soil water content and the weight of coarse organic litter (〉2mm) were consistently higher in middens than in bulk soil. Total C and N concentrations, C:N ratios, and microbial activity also were greatest in midden soil. Concentrations of ammonium-nitrogen and dissolved organic N were greater in middens than in bulk soil on most dates, suggesting accelerated decomposition and mineralization in middens. However, concentrations of nitrate were usually lower in middens, indicating reduced nitrification or increased leaching and denitrification losses from middens, relative to bulk soil. Fungal activity, as well as total microbial activity, was consistently greater in middens. The contribution of fungae to overall microbial activity differed significantly between middens and bulk soil only on one date when both soils were very dry; the contribution of fungae to microbial activity was lower in the middens on this date. We conclude that the midden-forming activity of L. terrestris can be a major determinant of spatial heterogeneity in some agricultural soils, and that this can potentially affect overall rates of soil processes such as organic matter decomposition, N mineralization, denitrification, and leaching.
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  • 16
    ISSN: 1432-0789
    Keywords: Key words Collembola ; Acari ; Araneae ; Nitrogen ; Stratification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper addresses the abundance, biomass and microstratification of functional groups of micro- and mesoarthropods inhabiting the organic layers of a Scots pine forest (Pinus sylvestris L.). An experiment using stratified litterbags, containing organic material of four degradation stages, i.e., freshly fallen litter, litter, fragmented litter and humus, was performed over a period of 2.5 years. Statistical data analysis revealed that each organic layer had a different, characteristic species composition that changed with time following successive degradation stages. Species of Acari, Araneae and Collembola were assigned to different functional groups based on taxonomy, microstratification, food type or feeding mode. The abundance and biomass carbon of functional groups were dependent on the organic layer and most functional groups showed a particular preference for one of the upper organic layers. Temporal and spatial differences in density and biomass carbon of functional groups could partly be related to fluctuations in the soil climate, although effects of trophic interactions could not be ruled out. A general decline in abundance and biomass, especially in populations of fungal feeders, during the last year of the study could not be explained by a reduction in litterbag volume, changed litter chemistry or soil climate, but was attributed to an indirect effect of a remarkable increase in soil coverage by wavy hair grass, Deschampsia flexuosa (L.). The analysis demonstrated that species diversity, microhabitat specification, soil fauna succession, and degradation stages of organic material are interrelated. The results obtained indicate that both the chemistry of organic matter and decomposition rates have an important effect on trophic relationships and community structure.
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  • 17
    ISSN: 1432-0789
    Keywords: Key words Methane oxidation ; Nitrogen ; Fertilizer ; Soils ; Isotopic dilution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The short-term effects of N addition on CH4 oxidation were studied in two soils. Both sites are unfertilized, one has been under long-term arable rotation, the other is a grassland that has been cut for hay for the past 125 years. The sites showed clear differences in their capacity to oxidise CH4, the arable soil oxidised CH4 at a rate of 0.013 μg CH4 kg–1 h–1 and the grassland soil approximately an order of magnitude quicker. In both sites the addition of (NH4)2SO4 caused an immediate reduction in the rate of atmospheric CH4 oxidation approximately in inverse proportion to the amount of NH4 + added. The addition of KNO3 caused no change in the rate of CH4 oxidation in the arable soil, but in the grassland soil after 9 days the rate of CH4 oxidation had decreased from 0.22 μg CH4 kg–1 h–1 to 0.13 μg CH4 kg–1 h–1 in soil treated with the equivalent of 192 kg N ha–1. A 15N isotopic dilution technique was used to investigate the role of nitrifiers in regulating CH4 oxidation. The arable soil showed a low rate of gross N mineralisation (0.67 mg N kg–1 day–1), but a relatively high proportion of the mineralised N was nitrified. The grassland soil had a high rate of gross N mineralisation (18.28 mg N kg–1 day–1), but negligible nitrification activity. It is hypothesised that since there was virtually no nitrification in the grassland soil then CH4 oxidation at this site must be methanotroph mediated.
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  • 18
    ISSN: 1573-143X
    Keywords: Cage culture ; Dietary lipid ; Dietary water ; Feeding frequency ; Moist diets ; Nitrogen ; Phosphorus ; Rainbow trout (Oncorhynchus mykiss)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The nutrient losses into the water from rainbow trout (Oncorhynchus mykiss) cage culture using locally caught low-fat Baltic herring, herring-based moist diets and fishmeal-based dry diets were estimated. Feeding with herring led to nitrogen and phosphorus losses into the water twice as high as those feeding with dry pellets (78–162 versus 37–39 g N and 15–39 versus 7–18 g P per kg growth). This was supported by direct measurements of ammonia and phosphate excretion. Increasing feeding frequencies resulted in increased nutrient losses irrespective of diet. Increasing dietary lipid level had a more pronounced effect in reducing the expected nutrient losses in dry pellets than herring. The reduction within the herring was approximately 18% on average for nitrogen and 25% for phosphorus losses. Dietary water content did not affect the nutrient losses. © Rapid Science Ltd. 1998
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  • 19
    ISSN: 0931-1890
    Keywords: Key words Pinus leucodermis ; Photosynthesis ; Respiration ; Nitrogen ; Chlorophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Pinus heldreichii Christ is a long-lived, slow-growing Tertiary relict from the Balkans. In this study we evaluated the physiological characteristics of eight needle-age classes of P. heldreichii grown at the Arboretum of the Institute of Dendrology in Kórnik, Poland. At the end of the growing season, current-year foliage had the highest rates of mass-based light-saturated net photosynthesis (Asat) of 33.5 nmol CO2· g–1· s–1. Asat decreased with needle age, but older needle classes retained from approximately 62 to 26% of the current needles’ rate. The relationship between leaf N and chlorophyll a concentration among all needle-age classes was highly significant (r = 0.96, P = 0.0006). The variation in Asat of 1- to 7-year-old needles was linearly related to needle N concentration (r = 0.98, P = 0.0001). Needle dark respiration rates among these needle age classes ranged from 0.8 to 2.2 nmol · g–1· s–1 and decreased with needle age and nitrogen concentration. Total phenols and glucose concentrations increased linearly with needle age. A similar pattern was observed in acid buffering capacity and the pH of tissue homogenates. The water content ranged from 62% for the current needles to 51% for the 6-year-old needles. Greater investment in leaf structural tissue and increased chemical defense is associated with higher structural cost of older needles and may reduce their photosynthetic activity. Significant declines in water and nitrogen content with needle age and an increase in content of phenolics is most likely a defense adaptation of P. heldreichii related to the species’ long-lived leaves.
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  • 20
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    Biology and fertility of soils 25 (1997), S. 296-301 
    ISSN: 1432-0789
    Keywords: Key words Methane ; Forest soil ; pH ; Liming ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Methane uptake to soil was examined in individual chambers at three small forest catchments with different treatments, Control, Limed and Nitrex sites, where N-deposition was experimentally increased. The catchments consisted of both well-drained forest and wet sphagnum areas, and showed uptake of CH4 from the ambient air. The lowest CH4 uptakes were observed in the wet areas, where the different treatments did not influence the uptake rate. In the well-drained areas the CH4 uptakes were 1.6, 1.4 and 0.6 kg ha–1 year–1 for the Limed, Control and Nitrex sites, respectively. The uptake of methane at the well-drained Nitrex site was statistically smaller than at the other well-drained catchments. Both acidification and increase in nitrogen in the soil, caused by the air-borne deposition, are the probable cause for the reduction in the methane uptake potential. Uptake of methane was correlated to soil water content or temperature for individual chambers at the well-drained sites. The uptake rate of methane in soil cores was largest in the 0- to 10-cm upper soil layer. The concentration of CH4 in the soil was lower than the atmospheric concentration up to 30 cm depth, where methane production occurred. Besides acting as a sink for atmospheric methane, the oxidizing process in soil prevents the release of produced methane from deeper soil layers reaching the atmosphere.
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  • 21
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    Biology and fertility of soils 25 (1997), S. 366-371 
    ISSN: 1432-0789
    Keywords: Key words Water addition ; Nitrogen ; Glucose ; O2 content ; Temperature ; Closed-chamber method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Emission of N2O from cultivated and fertilised soils may contribute significantly to the total global N2O emission. This study included laboratory and field investigations of the N2O production from a dry stubble field as influenced by addition of water, nitrogen and glucose. N2O fluxes were measured using a closed-chamber technique, and the O2 content in the soil was measured using soil probes. Results from a laboratory soil core technique were correlated to the relative N2O emission observed in the field. When the soil water content in the field increased from 14% to 60% water-filled pore space, the N2O emission increased from non-significant to a constant emission of 30 μg N m–2 h–1. At this soil water content the production of N2O was limited by the availability of nitrogen and carbon. Application of nitrogen at soil temperatures of 13 and 21°C in a pre-wetted soil increased the N2O emission 3.1- and 3.7-fold, respectively, whereas nitrogen plus carbon application increased the N2O emission 13.3- and 7.3-fold, respectively. In both treatments the N2O emission rates were affected by fluctuations in soil temperature and O2 content. The results indicate that even in a soil producing very little N2O under dry conditions, the soil microbial community maintains a potential to produce N2O when favourable conditions occur in terms of availability of water, nitrogen and carbon.
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  • 22
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    Journal of agricultural and environmental ethics 10 (1997), S. 249-267 
    ISSN: 1573-322X
    Keywords: Animals ; Asia ; consciousness ; Australia ; Hong Kong ; India ; Israel ; Japan ; New Zealand ; The Philippines ; Russia ; Singapore ; Thailand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Philosophy
    Notes: Abstract The interactions between humans, animals and the environment have shaped human values and ethics, not only the genes that we are made of. The animal rights movement challenges human beings to reconsider interactions between humans and other animals, and maybe connected to the environmental movement that begs us to recognize the fact that there are symbiotic relationships between humans and all other organisms. The first part of this paper looks at types of bioethics, the implications of autonomy and the value of being alive. Then the level of consciousness of these relationships are explored in survey results from Asia and the Pacific, especially in the 1993 International Bioethics Survey conducted in Australia, Hong Kong, India, Israel, Japan, New Zealand, The Philippines, Russia, Singapore and Thailand. Very few mentioned animal consciousness in the survey, but there were more biocentric comments in Australia and Japan; and more comments with the idea of harmony including humans in Thailand. Comparisons between questions and surveys will also be made, in an attempt to describe what people imagine animal consciousness to be, and whether this relates to human ethics of the relationships.
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  • 23
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    Biology and fertility of soils 21 (1996), S. 114-120 
    ISSN: 1432-0789
    Keywords: Statistical methods ; Mineralization ; Nitrogen ; First-order kinetics ; Incubation experiment ; Model for N mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Potentially mineralizable soil N was determined after incubation for 2, 4, 8, 12, 16, 22, and 30 weeks, according to the Stanford and Smith method. A first-order kinetics model was used, and a simulation study was performed using three different statistical methods to estimate potentially mineralizable N and the rate constant k. The first method was based on the maximum-likelihood approach. The second one relied on nonlinear least square data fitting. The third method was based on linear of logarithmically transformed data. The results of the simulation study suggested that the non-linear least square method was preferable to the others. This method was then applied to real data from 30 different Italian soils. The values obtained for potentially mineralizable N were, on average, 10% of total N (mean standard error=0.9). The estimated value of k was 0.050 (mean standard error=0.005). Finally, from the values obtained for k and the results of the simulation, the results indicated that significantly less reliable estimates of potentially mineralizable N were obtained by using data for up to only 22 weeks of incubation.
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  • 24
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    Biology and fertility of soils 22 (1996), S. 1-9 
    ISSN: 1432-0789
    Keywords: Key words Microbial Biomass ; Carbon ; Nitrogen ; Chloroform-fumigation extraction ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory studies were conducted to determine C and N dynamics during the decomposition of ryegrass straw under mesophilic and thermophilic conditions. A KC of 0.61 was developed for the chloroform-fumigation extraction method to estimate microbial biomass C. These estimates showed that the C and N requirement of the thermophilic biomass was approximately 50% of the mesophilic biomass. There was no relationship between chloroform-fumigation microbial biomass estimates and plating of microorganisms from straw on specific media. Mineralized C was measured as 185 and 210 g kg–1 straw in the 25°C and 50°C treatments, respectively. The efficiency of microbial substrate use, on a total straw basis, was 34 and 28% in the 25°C and 50°C incubations, respectively. The level of soluble C declined more slowly than total C mineralization at both temperatures, indicating that a portion of the labile C was not readily biodegradable. The addition of N decreased the rate of C mineralization at both temperatures. The reduced N requirement of the thermophiles explains why rapid degradation of the high C:N residue occurred without additional N or the need for the addition of a low C:N ratio substrate. Additional inoculum did not affect the decomposition process. We conclude that the promotion of thermophilic biomass activities, through composting for example, may prove useful in upgrading agricultural wastes for introduction into sustainable cropping systems.
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  • 25
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    Biology and fertility of soils 22 (1996), S. 184-190 
    ISSN: 1432-0789
    Keywords: Key words Cropping systems ; Soil organic matter ; Nitrogen ; Phosphorus ; Potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of up to 23 years of agricultural cropping of a boreal forest soil on soil organic carbon (SOC) and N, P, and K pools were studied. The cropping systems studied were: (a) continuous barley, (b) continuous forage bromegrass, (c) continuous forage legume, and (d) barley/grass-legume forage rotation. Continuous bromegrass increased while other cropping systems decreased SOC in the surface soil. Kjeldahl N in soil approximately followed the trend in SOC. The net gain in N under continuous grass was attributed mostly to nonsymbiotic N fixation. Changes in SOC content appeared to be also influenced by cropping and tillage frequencies. Changes in fixed (intercalary) ammonium were small. There was no measurable change in total P, in part, because input was only slightly higher than crop offtake. Organic P increased under continuous bromegrass, and tended to decrease under continuous legume. The C/N and C/P ratios of soil organic matter decreased slightly with cropping. Exchangeable K (Kex) was decreased by cropping systems containing a legume crop to a greater extent than those without a legume crop. Most of the decrease occurred in the 0–15 cm depth. Nitric acid extractable K was not affected by cropping. Since net loss of Kex to 30 cm depth was substantially less than crop offtake, it is suggested that subsoil K reserves and matrix K were supplying a major portion of the crops‘ K requirement. It is concluded that the effects of cropping systems on SOC, N, P and K are influenced by crop type, and cropping and tillage frequencies.
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  • 26
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    Biology and fertility of soils 22 (1996), S. 1-9 
    ISSN: 1432-0789
    Keywords: Microbial Biomass ; Carbon ; Nitrogen ; Chloroform-fumigation extraction ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory studies were conducted to determine C and N dynamics during the decomposition of ryegrass straw under mesophilic and thermophilic conditions. A KC of 0.61 was developed for the chloroform-fumigation extraction method to estimate microbial biomass C. These estimates showed that the C and N requirement of the thermophilic biomass was approximately 50% of the mesophilic biomass. There was no relationship between chloroform-fumigation microbial biomass estimates and plating of microorganisms from straw on specific media. Mineralized C was measured as 185 and 210 g kg-1 straw in the 25°C and 50°C treatments, respectively. The efficiency of microbial substrate use, on a total straw basis, was 34 and 28% in the 25°C and 50°C incubations, respectively. The level of soluble C declined more slowly than total C mineralization at both temperatures, indicating that a portion of the labile C was not readily biodegradable. The addition of N decreased the rate of C mineralization at both temperatures. The reduced N requirement of the thermophiles explains why rapid degradation of the high C:N residue occurred without additional N or the need for the addition of a low C:N ratio substrate. Additional inoculum did not affect the decomposition process. We conclude that the promotion of thermophilic biomass activities, through composting for example, may prove useful in upgrading agricultural wastes for introduction into sustainable cropping systems.
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  • 27
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    Biology and fertility of soils 22 (1996), S. 184-190 
    ISSN: 1432-0789
    Keywords: Cropping systems ; Soil organic matter ; Nitrogen ; Phosphorus ; Potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of up to 23 years of agricultural cropping of a boreal forest soil on soil organic carbon (SOC) and N, P, and K pools were studied. The cropping systems studied were: (a) continuous barley, (b) continuous forage bromegrass, (c) continuous forage legume, and (d) barley/grass-legume forage rotation. Continuous bromegrass increased while other cropping systems decreased SOC in the surface soil. Kjeldahl N in soil approximately followed the trend in SOC. The net gain in N under continuous grass was attributed mostly to nonsymbiotic N fixation. Changes in SOC content appeared to be also influenced by cropping and tillage frequencies. Changes in fixed (intercalary) ammonium were small. There was no measurable change in total P, in part, because input was only slightly higher than crop offtake. Organic P increased under continuous bromegrass, and tended to decrease under continuous legume. The C/N and C/P ratios of soil organic matter decreased slightly with cropping. Exchangeable K (Kex) was decreased by cropping systems containing a legume crop to a greater extent than those without a legume crop. Most of the decrease occurred in the 0–15 cm depth. Nitric acid extractable K was not affected by cropping. Since net loss of Kex to 30 cm depth was substantially less than crop offtake, it is suggested that subsoil K reserves and matrix K were supplying a major portion of the crops' K requirement. It is concluded that the effects of cropping systems on SOC, N, P and K are influenced by crop type, and cropping and tillage frequencies.
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  • 28
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    Biology and fertility of soils 22 (1996), S. 40-44 
    ISSN: 1432-0789
    Keywords: Key words Northern hardwoods ; Disturbance in soil ; Nitrogen ; Soil warming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Installation of heating cables for warming soil was used to evaluate the effect of disturbance on soil solution chemistry within a northern hardwood forest (Adirondack Mountains, New York). Differences in response among treatments suggested the importance of both the depth and timing of cable installation. There were increases (p〉0.05) in many solutes within pilot study plots in which “surrogate cable” was installed at 15 cm depth. Most notably, mean nitrate concentrations for the 1st year following disturbance were 744 μeq l–1 at 15 cm depth compared to 7 μeq l–1 for the non-disturbed control. A comparison of pilot plots with 5 cm cable depth and an unheated soil-warming control plot with the same cable disturbance showed that the seasonality of soil disturbance may have a key role in response to disturbance. The soil solution response was diminished if installation occurred during the spring, a period of rapid uptake of nitrogen by vegetation. Mean nitrate concentrations were 176 μeq l–1 for 5-cm pilot plots (installed in fall 1991) versus 6 μeq l–1 for 5-cm, unheated soil-warming control plots (installed in spring 1992). Disturbance effects were attenuated over time and not generally apparent 1 year after installation.
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  • 29
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    Biology and fertility of soils 22 (1996), S. 40-44 
    ISSN: 1432-0789
    Keywords: Northern hardwoods ; Disturbance in soil ; Nitrogen ; Soil warming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Installation of heating cables for warming soil was used to evaluate the effect of disturbance on soil solution chemistry within a northern hardwood forest (Adirondack Mountains, New York). Differences in response among treatments suggested the importance of both the depth and timing of cable installation. There were increases (p〉0.05) in many solutes within pilot study plots in which “surrogate cable” was installed at 15 cm depth. Most notably, mean nitrate concentrations for the 1st year following disturbance were 744 μeq l-1 at 15 cm depth compared to 7 μeq l-1 for the non-disturbed control. A comparison of pilot plots with 5 cm cable depth and an unheated soil-warming control plot with the same cable disturbance showed that the seasonality of soil disturbance may have a key role in response to disturbance. The soil solution response was diminished if installation occurred during the spring, a period of rapid uptake of nitrogen by vegetation. Mean nitrate concentrations were 176 μeq l-1 for 5-cm pilot plots (installed in fall 1991) versus 6 μeq l-1 for 5-cm, unheated soil-warming control plots (installed in spring 1992). Disturbance effects were attenuated over time and not generally apparent 1 year after installation.
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  • 30
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    Biology and fertility of soils 23 (1996), S. 399-404 
    ISSN: 1432-0789
    Keywords: Key words Snails ; Nitrogen ; Desert ; Mineralization ; Nitrification ; Respiration ; Feces ; N cycling processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Snail grazing and feces production have been shown to be major components of the nitrogen (N) budget of Negev Desert ecosystems. However, the movement of N from feces into soil N cycling processes has not been studied. In this study, we measured immediate N release from different types of snail feces following wetting of dry desert soils, and characterized potential net N mineralization and nitrification and soil respiration over a 12-day incubation under laboratory conditions. The dynamics of inorganic N exhibited two distinct phases during the 12-day incubation: (1) immediate release of inorganic N following wetting of the soil and (2) decline of inorganic N from day 1 to day 12 of the incubation. The immediate pulse of N release from this one wetting event (6–25 mg N m–2) was larger than annual atmospheric inputs of N to Negev Desert ecosystems (〈2 mg N m–2); however, from 50 to 80% of the N released upon wetting was consumed by the end of the incubation. There were differences in inorganic N release and respiration from feces from different kinds of snails, and from feces from the same species of snail fed different plants. The results suggest that while snail feces contribute significant amounts of plant available N to Negev ecosystems, plants must compete with other “sinks” for this N.
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  • 31
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    Biology and fertility of soils 23 (1996), S. 399-404 
    ISSN: 1432-0789
    Keywords: Snails ; Nitrogen ; Desert ; Mineralization ; Nitrification ; Respiration ; Feces ; N cycling processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Snail grazing and feces production have been shown to be major components of the nitrogen (N) budget of Negev Desert ecosystems. However, the movement of N from feces into soil N cycling processes has not been studied. In this study, we measured immediate N release from different types of snail feces following wetting of dry desert soils, and characterized potential net N mineralization and nitrification and soil respiration over a 12-day incubation under laboratory conditions. The dynamics of morganic N exhibited two distinct phases during the 12-day incubation: (1) immediate release of inorganic N following wetting of the soil and (2) decline of inorganic N from day 1 today 12 of the incubation. The immediate pulse of N release from this one wetting event (6–25 mg N m-2) was larger than annual atmospheric inputs of N to Negev Desert ecosystems (〈2 mg N m-2); however, from 50 to 80% of the N released upon wetting was consumed by the end of the incubation. There were differences in inorganic N release and respiration from feces from different kinds of snails, and from feces from the same species of snail fed different plants. The results suggest that while snail feces contribute significant amounts of plant available N to Negev ecosystems, plants must compete with other “sinks” for this N.
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  • 32
    ISSN: 0931-1890
    Keywords: Key words Conifer ; Fluoride ; Nitrogen ; Sulphur dioxide ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Effects of SO2, aqueous fluoride (NaF) and a solution of nitrogen compounds (NH4NO3) on the visible symptoms, pollutant accumulation and ultrastructure of Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.] seedlings were studied in an open-air experiment lasting for 3 consecutive years. Visible injury symptoms were most pronounced in combination exposures and whenever F was applied. Visible symptoms correlated well with needle pollutant concentrations. Exposure to NaF increased needle F contents particularly when F was applied with SO2 or NH4NO3. This suggests that a reduction in N or SO2 emissions, in F polluted areas, could improve the condition of conifers via decreased accumulation of phytotoxic F in the needles. Norway spruce needles accumulated 2 – 10 times as much S and F as those of Scots pine. Microscopic observations showed various changes in the needle mesophyll cell ultrastructure. In both species, exposure to SO2 increased significantly the amount of cytoplasmic vacuoles, suggesting detoxification of excess sulphate or low pH. F treatments resulted in a significant enlargement of plastoglobuli in Scots pine and a darkening of plastoglobuli in Norway spruce. All exposures enhanced the accumulation of lipid bodies. An increased portion of translucent plastoglobuli was most pronounced in N treatments. Many of the ultrastructural changes and visible symptoms appeared only as number of years exposed increased, indicating that long-term experiments are needed. Both visible symptoms and ultrastructural changes pointed to the more pronounced sensitivity of Norway spruce compared to Scots pine. Ultrastructural results mostly supported earlier qualitative observations of F, N and SO2 effects on needle mesophyll cell ultrastructure. However, no reduction of thylakoids in SO2 containing exposure or curling of thylakoids in F exposure could be detected in the present study.
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  • 33
    ISSN: 0931-1890
    Keywords: Keywords Amino-acids ; Carbohydrates ; Cell compounds ; Nitrogen ; Rhododendron ferrugineum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  This study evaluates the utility of cell compounds as indicators of nutrition status of plant populations. An overview of the soluble free amino-acids, carbohydrates and P-compounds in the two year classes of leaves from Rhododendron ferrugineum populations showing variable biological performances, was drawn up using carbon-13 and phosphorus-31 nuclear magnetic resonance spectroscopy (NMR). The results showed differences between the age of leaves and the degree of population closure. The open population, which has the smallest growth rate and net primary productivity, had generally lower levels of amino-acids but higher levels of carbohydrates and P-compounds. Neither the amounts of mineral nitrogen produced by the soils nor the total nitrogen concentrations in leaves differed significantly. Still we hypothesize that the nitrogen availability could be largely responsible for the variations observed between the populations, as phosphorus analyses showed that the two populations did not suffer significant P deficiencies. Differences in vitality of R. ferrugineum may be explained by the fact that in an open population R. ferrugineum is forced into a situation of sharing nutrients with other species while in a closed population it is the sole species to exploit a specific pool of nutrients. Finally we observed that the 13C- and 31P-NMR approach is more suitable for studying the nutrition status of plant populations under field conditions than the determination of the total amounts of different elementary nutrients.
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  • 34
    ISSN: 1432-0789
    Keywords: Carbon ; Coffee pulp ; Eisenia fetida ; Nitrogen ; Nutrients ; Vermicomposting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In Colombia, more than 1 million tons of coffee pulp are produced every year. Its transformation into compost by means of turned piles has led to a final product with poor physical and chemical characteristics and vermicomposting has been suggested as an alternative method of transforming these wastes into a useful organic fertilizer. The ability of the earthworm Eisenia fetida to transform coffee pulp into a valuable compost was evaluated. The influence of bed depth and time on different C fractions, N content and availability of nutrients was studied. The results showed that the C and N contents were not affected by the depth of the bed, whereas time affected both. An increase in the fractionation ratio, determined by calculating the C in the fraction smaller than 100 μm as a percentage of C in the samples as a whole, and low values of humic-like substances were recorded during vermicomposting. After ingestion of the pulp by the earthworms, an increase in available P, Ca, and Mg but a decrease in K were detected.
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  • 35
    ISSN: 1432-0789
    Keywords: Key words Carbon ; Coffee pulp ; Eisenia fetida ; Nitrogen ; Nutrients ; Vermicomposting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In Colombia, more than 1 million tons of coffee pulp are produced every year. Its transformation into compost by means of turned piles has led to a final product with poor physical and chemical characteristics and vermicomposting has been suggested as an alternative method of transforming these wastes into a useful organic fertilizer. The ability of the earthworm Eisenia fetida to transform coffee pulp into a valuable compost was evaluated. The influence of bed depth and time on different C fractions, N content and availability of nutrients was studied. The results showed that the C and N contents were not affected by the depth of the bed, whereas time affected both. An increase in the fractionation ratio, determined by calculating the C in the fraction smaller than 100 μm as a percentage of C in the samples as a whole, and low values of humic-like substances were recorded during vermicomposting. After ingestion of the pulp by the earthworms, an increase in available P, Ca, and Mg but a decrease in K were detected.
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  • 36
    ISSN: 1432-2285
    Keywords: Conifer ; Fluoride ; Nitrogen ; Sulphur dioxide ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of SO2, aqueous fluoride (NaF) and a solution of nitrogen compounds (NH4NO3) on the visible symptoms, pollutant accumulation and ultrastructure of Scots pine (Pinus sylvestris L.) and Norway spruce [Picea abies (L.) Karst.] seedlings were studied in an open-air experiment lasting for 3 consecutive years. Visible injury symptoms were most pronounced in combination exposures and whenever F was applied. Visible symptoms correlated well with needle pollutant concentrations. Exposure to NaF increased needle F contents particularly when F was applied with SO2 or NH4NO3. This suggests that a reduction in N or SO2 emissions, in F polluted areas, could improve the condition of conifers via decreased accumulation of phytotoxic F in the needles. Norway spruce needles accumulated 2–10 times as much S and F as those of Scots pine. Microscopic observations showed various changes in the needle mesophyll cell ultrastructure. In both species, exposure to SO2 increased significantly the amount of cytoplasmic vacuoles, suggesting detoxification of excess sulphate or low pH. F treatments resulted in a significant enlargement of plastoglobuli in Scots pine and a darkening of plastoglobuli in Norway spruce. All exposures enhanced the accumulation of lipid bodies. An increased portion of translucent plastoglobuli was most pronounced in N treatments. Many of the ultrastructural changes and visible symptoms appeared only as number of years exposed increased, indicating that long-term experiments are needed. Both visible symptoms and ultrastructural changes pointed to the more pronounced sensitivity of Norway spruce compared to Scots pine. Ultrastructural results mostly supported earlier qualitative observations of F, N and SO2 effects on needle mesophyll cell ultrastructure. However, no reduction of thylakoids in SO2 containing exposure or curling of thylakoids in F exposure could be detected in the present study.
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  • 37
    ISSN: 1432-2285
    Keywords: Nitrogen ; Picea sitchensis ; Relative growth rates ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seedlings ofPicea sitchensis, Thuja plicata andTsuga heterophylla were supplied N hydroponically at one of four exponentially increasing rates of addition (0.09, 0.07, 0.05, or 0.025 gN-1 day-1) for up to 3 months in a naturally illuminated glasshouse. Relative growth rates (RGR) were analyzed as a function of N uptake, the allocation of assimilated N to foliage (LNFR), foliar N concentrations (Nla) and met assimilation rates (NAR), which were combined to estimate N productivity (RGR per unit whole-plant N concentration). Nitrogen accumulation, biomass and N partitioning and RGR and its components varied with species in response to the different N regimes.T. heterophylla had the lowest maximum wholeplant N concentrations (wpN) and specific absorption rates for N and exhibited the least plasticity in root: shoot ratios as wpN increased from 11–21 mg g-1. In all species, RGR increased linearly with wpN, while LNFR increased curvilinearly. Foliar N (Nla) increased linearly with wpN and NAR increased linearly with Nla. The RGRs ofT. heterophylla were highest at wpNs up to 18 mg g-1, a result of higher foliar N use efficiencies (NAR/Nla). However, RGR increased more with wpN inT. plicata andP. sitchensis. Although LNFR increased with wpN in all species, foliar N use efficiency declined, possibly due to an increased partitioning of foliar soluble N to non-photosynthetic compounds. Thus, in each species, N productivity did not increase above intermediate levels of wpN: 14 mg g-1 inT. heterophylla, 16 mg g-1 inP. sitchensis and 17 mg g-1 inT. plicata.
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  • 38
    ISSN: 1432-2285
    Keywords: Nitrogen ; Photosynthesis ; Picea sitchensis ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of differing, exponentially increasing rates of N addition (0.025, 0.05, 0.07 and 0.09 gN gN-1day-1) on photosynthesis, discrimination against13C and partitioning of foliar N to chlorophyll and major photosynthetic proteins were compared in seedlings of the evergreen conifersPicea sitchensis, Thuja plicata andTsuga heterophylla. T. heterophylla had the lowest range of foliar N concentrations (Nlm). Across species, photosynthetic rates (A) increased linearly with Nlm to a maximum at 21 mg g-1 and declined at higher Nlms. Species differences inA resulted from differences in Nlm, not from differences in photosynthetic N use efficiency. Self-shading may have causedA to decline at a high Nlm inP. sitchensis andT. plicata. Measurements of gas exchange and δ13C suggested that carboxylation capacity increased more than did stomatal conductance as Nlm increased. The responses were small and confined to Nlms associated with the lesser rates of N addition. Concentrations of total protein, ribulose 1,5-bisphosphate carboxylase (RUBISCO) and the light harvesting chlorophyll a/b protein complex (LHC) increased with Nlm, but the fraction of foliar N allocated to RUBISCO and LHC increased with Nlm only inP. sitchensis and only between the 0.025 and 0.05N regimes. The responsiveness ofA and concentrations of RUBISCO to Nlm were less than reported for deciduous C3 species.
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  • 39
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    Journal of plant growth regulation 15 (1996), S. 159-165 
    ISSN: 1435-8107
    Keywords: Germination ; Gibberellin ; Imbibition ; Lettuce ; Nitrogen ; Phytochrome ; Skotodormant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Skotodormant seeds of Lactuca sativa Grand Rapids imbibed in darkness for 10 days (10-day DS) germinated poorly upon terminal treatment with red light (R) or gibberellin A3 (GA3). Inorganic nitrogen salts in the imbibition solutions reduced seed skotodormancy. Ten-day DS seeds, imbibed in 25 mm salt solutions followed by terminal R, germinated 99% if imbibed in NH4NO3, 70% if imbibed in KNO3 or NH4Cl, and 55% if imbibed in NaNO3. Seeds imbibed in higher salt concentrations germinated fully upon terminal R treatment. Seeds imbibed in 25 mm NH4Cl or in 50 mm NH4NO3 germinated completely upon GA3 treatment. Osmotic effects of imbibition media accounted for only part of the effect, since seeds imbibed in 50 mm CaCl2 or NaCl germinated poorly following R or GA3 treatment. Seeds imbibed in 500 mm polyethylene glycol (PEG) 1000 or mannitol solutions for 10 days still exhibited skotodormancy. Treatments of R or GA3 did not stimulate germination in seeds imbibed in mannitol, but germination was complete if seeds were given 1-h acid immersion plus a water rinse before the terminal R or GA3 treatment. Seeds imbibed in 50–500 mm PEG during 10-day DS germinated significantly better in response to terminal R. Terminal GA3 significantly improved germination only in seeds imbibed at 500 mm PEG. Pfr appeared to function in mannitol-imbibed seed only after an acid treatment. Seed exposure to inorganic nitrogen salts during the 10-day DS maintained seed sensitivity to terminal R or GA3 treatment. The depth of seed skotodormancy was related to the availability of inorganic nitrogen and also involved the levels of Pfr or endogenous GA3.
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  • 40
    ISSN: 1573-0867
    Keywords: China ; Loess Plateau ; maize ; 15N ; Nitrogen ; urea ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Field trials were carried out to study the fate of15N-labelled urea applied to summer maize and winter wheat in loess soils in Shaanxi Province, north-west China. In the maize experiment, nitrogen was applied at rates of 0 or 210 kg N ha−1, either as a surface application, mixed uniformly with the top 0.15 m of soil, or placed in holes 0.1 m deep adjacent to each plant and then covered with soil. In the wheat experiment, nitrogen was applied at rates of 0, 75 or 150 kg N ha−1, either to the surface, or incorporated by mixing with the top 0.15 m, or placed in a band at 0.15 m depth. Measurements were made of crop N uptake, residual fertilizer N and soil mineral N. The total above-ground dry matter yield of maize varied between 7.6 and 11.9 t ha−1. The crop recovery of fertilizer N following point placement was 25% of that applied, which was higher than that from the surface application (18%) or incorporation by mixing (18%). The total grain yield of wheat varied between 4.3 and 4.7 t ha−1. In the surface applications, the recovery of fertilizer-derived nitrogen (25%) was considerably lower than that from the mixing treatments and banded placements (33 and 36%). The fertilizer N application rate had a significant effect on grain and total dry matter yield, as well as on total N uptake and grain N contents. The main mechanism for loss of N appeared to be by ammonia volatilization, rather than leaching. High mineral N concentrations remained in the soil at harvest, following both crops, demonstrating a potential for significant reductions in N application rates without associated loss in yield.
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  • 41
    ISSN: 1432-0789
    Keywords: Excreta ; Fertiliser ; Microbial biomass ; Nitrogen ; Silvopastoral
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This paper describes a field study to assess the effect of increasing the frequency of split applications of N fertiliser on the pattern of plant uptake, soil N availability, and microbial biomass C and N. Measurements were taken during the growing season in different positions relative to young trees (Prunus avium L.) in an upland silvopastoral system in its first year after establishment. At fertiliser rates of 72 and 144 kg ha-1 N applied as NH4NO3, increasing the number of split applications increased N uptake by the pasture. Mineral forms of soil N measured 2 weeks after application indicated that residual NH inf4 sup+ -N and total mineral N were also greater in this treatment on certain dates. Soil NO inf3 sup- -N was positively correlated with the soil moisture content, and nitrification reached a maximum in early May and declined rapidly thereafter except within the herbicide-treated areas around the trees where soil moisture had been conserved. Results of the study suggest that high NO inf3 sup- -N in herbicide-treated areas was probably caused by mineralisation of grass residues and low uptake by the tree rather than by preferential urine excretion by sheep sheltering beside the trees. Mean microbial biomass C and N values of 894 and 213 kg ha-1, respectively, were obtained. Microbial C was slightly increased by the higher frequency of split applications at 144 kg ha-1 N and was probably related to the greater herbage production with this treatment. Microbial N was not significantly affected by the N treatments. Both microbial biomass C and N increased during the growing season, resulting in the net immobilisation of at least 45 kg ha-1 N which was later released during the autumn.
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  • 42
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    Biology and fertility of soils 20 (1995), S. 237-242 
    ISSN: 1432-0789
    Keywords: Mineralization capacity ; Nitrogen ; Soil incubation ; Time of incubation ; Temperate humid-zone soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The N mineralization rate in 11 soils was studied by aerobic incubation at 28°C and at a moisture content of 75% of field capacity for 2 weeks (short term) and 6 weeks (medium term). Relationships between the N mineralization indices for each period were evaluated. Ammonification largely predominated during the first 2 weeks of incubation, whereas nitrification was the predominant process between weeks 2 and 6. The net N mineralized in the different soils varied from 0 to 2.85% of the organic N after 2 weeks of incubation and from 0.32 to 3.36% of the organic N after 6 weeks of incubation, the mean values for each period being 0.82 and 1.51% of the organic N, respectively. The quantities of NH inf4 sup+ -N, NO inf3 sup- -N, and total inorganic N produced and the percentage of organic N mineralized after 2 weeks of incubation were highly and positively correlated with the coresponding values after 6 weeks of incubation. These results showed that either length of incubation could be used to determine the potential N mineralization capacity of the soils. Information obtained from two incubation periods was largely supplementary for the kinetic study of N mineralization, ammonification, and nitrification; therefore a medium-term incubation with intermediate measurements of N mineralization over a short term may be more useful than a single measurement using either of the two incubation periods.
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  • 43
    ISSN: 1432-2285
    Keywords: Amino acids ; Arginine ; Eucalyptus ; Foliage ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rates of growth of seedlings of E. globulus, E. regnans and E. nitens were related to phosphorus supply in two soils but concentrations of total nitrogen and total phosphorus in most plant tissues did not vary significantly among soil or phosphorus treatments. Differences in concentrations of nitrogen and phosphorus and in the composition of the pool of free amino-acids among leaves at different stages of development were far greater than differences between treatments. The most significant of these differences were several-fold greater concentrations of arginine in the oldest leaves and these are most likely due to protein degradation and/or in situ synthesis since arginine is not generally phloem mobile. The concentration of reduced nitrogen in xylem sap was inversely related to growth and glutamine was by far the dominant nitrogenous solute. We suggest that specific nitrogenous solutes may be useful indices of the nitrogen status of eucalypt tissues for insect herbivores.
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  • 44
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    Biology and fertility of soils 17 (1994), S. 159-166 
    ISSN: 1432-0789
    Keywords: Eucalypt forest ; Litter decomposition ; Fertilizer ; Nitrogen ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The decomposition and nutrient content of litter was studied for 2 years in regrowth Eucalyptus diversicolor forest to which N (0, 200 kg ha-1 year-1) and P (0, 30, 200 kg ha-1) had been applied. The P addition increased, and the N addition decreased, the rate of dry weight loss of decomposing litter. Analysis of the coefficients of a double exponential decay model with components describing the release of labile and resistant fractions indicated that decomposition of the resistant component of litter was most affected by the fertilizer additions. Treatment with N reduced the rate of loss of this component and increased its half-life by approximately 30%, whereas P treatment increased its rate of decay and decreased its half-life by approximately 30%. P accumulated in litter during decomposition. P uptake and retention was greater in P-treated than untreated plots. The application of N reduced P accumulation in litter. An accumulation of N also occurred during decomposition, the amount of N imported into litter being greater on plots treated with N fertilizer. Treatment with N affected the amount of S in decomposing litter. Litter on N-treated plots either accumulated more S or released it more slowly than litter on plots not treated with N. The application of N as NH4NO3 decreased forest-floor litter pH, increased litter layer mass (by 15%), and increased the amount of N (by 34%) and S (by 32%) stored in the forest floor. Treatment with P reduced the amount of N (by 22%) stored in the litter layer. The application of 200 kg P ha-1 in the absence of N increased the store of P in the litter layer by 80%, but when N and P were applied together the amount of P in the litter was not significantly different between P treatments.
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  • 45
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    Biology and fertility of soils 17 (1994), S. 173-176 
    ISSN: 1432-0789
    Keywords: Ammonification ; Cyfluthrin ; Nitrification ; Nitrogen ; N mineralization ; N transformations ; Pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory incubation experiments were conducted in soil to study the influence of the insecticide Baythroid on immobilization-remineralization of added inorganic N, mineralization of organic N, and nitrification of added NH inf4 su+ -N. Baythroid was applied at 0, 0.4, 0.8, 1.6, 3.2, and 6.4 μg g-1 soil (active ingredient basis). The treated soils were incubated at 30°C for different time intervals depending upon the experiment. The immobilization and mineralization of N were significantly increased in the presence of Baythroid, the effect being greater with higher doses of the insecticide. Conversely, nitrification was retarded at lower doses of Baythroid and significantly inhibited at higher doses. The results of these studies suggest that excessive amonts of insecticide residues affect different microbial populations differently, leading to changes in nutrient cycling.
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  • 46
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    Plant foods for human nutrition 46 (1994), S. 1-11 
    ISSN: 1573-9104
    Keywords: Chemical composition ; Cultivar ; Harvest data ; Lactuca sativa L. ; Lettuce ; Nitrate ; Nitrogen ; Plant age ; Tipburn ; Quality ; Vitamin C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The marketable and nutritional quality of crisphead lettuce as affected by nitrogen supply, cultivar, and plant age at harvest was investigated in six plantings during 1989 and 1990. The optimum yield of marketable heads was obtained at a total nitrogen supply of 150 kg N per ha although only small differences were observed to the yield at 100 and 200 kg total N per ha. The total nitrogen supply included the amount of mineral nitrogen within the rhizosphere. The incidence of dry tipburn in older leaves was clearly decreased by an increased nitrogen supply, especially at late planting. The content of nitrate was increased and the content of dry matter and vitamin C decreased with increased nitrogen supply. The vitamin C content was higher for the cultivar ‘Marius’ than for ‘Saladin’. As plants got older, the nutritional quality of crisphead lettuce decreased because the content of nutrients, especially vitamin C, decreased with increased plant age at harvest.
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  • 47
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    Biology and fertility of soils 15 (1993), S. 153-159 
    ISSN: 1432-0789
    Keywords: Calcium ; Maize ; Nitrogen ; Brazilian Amazon ; Cation leaching ; Canavalia ensiformes ; Mucuna aterrima
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This work investigated the effectsof amendments of fertilizer N and lime on subsoil acidity and maize rooting depth in an acid soil of the central Amazon basin. A split-plot designed field experiment was conducted on a clayey Oxisol (Typic Acrudox) during a 16-month period. Main plots received 0 or 4 Mt ha-1 of lime. Subplots were four crop sequences: (1) Maize-green manure (Canavalia ensiformes); (2) maize-green manure (Mucuna aterrima); (3) maize-bare fallow, with the maize receiving 300 kg ha-1 of urea-N; and (4) bare fallow, with an application of 300 kg ha-1 of urea-N at the same time as sequence 3. Plots were periodically sampled to 1.2 m. The experimental site received 4265 mm of precipitation during 16 months; approximately 60%–90% of this rain percolated through the profile. Substantial amounts of Ca were leached from the 0–30 cm horizon during the experimental period, but only limited amounts accumulated in the subsoil. Base saturation below 45 cm was less than 50% at the end of the experiment regardless of lime treatment. Roots of maize were concentrated in the 0–30 cm layers in limed plots and the 0–20 cm layers in unlimed plots. In all treatments less than 5% of the roots was found below 50 cm. An acidity balance indicated that considerable acidity was leached below the plow layer and out of the profile.
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  • 48
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    Trees 7 (1993), S. 86-91 
    ISSN: 1432-2285
    Keywords: Pinus radiata ; Stem deformation ; Nitrogen ; Stem form ; Elasticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seedlings from nine families of Pinus radiata were grown in a glasshouse under conditions of high and low nitrate nitrogen availability to investigate effects on anatomical and strength characteristics of stems. Families were classified into groups dependent upon their previously determined susceptibility to stem deformation prevalent in plantations established on fertile ex-pasture. Nitrogen treatments significantly affected seedling form in terms of both branch production and stem slenderness. The high N treatment resulted in shorter seedlings, a proportion of which were obviously stunted. Stem strength of seedlings, physically supported throughout the experiment, was assessed as stem lean at harvest as well as the bending strength of the fresh stem at 50% stem height. These two variables were found not to be correlated. Stem lean at harvest was greatest in families known to be susceptible to stem deformation. These families produced stems that were also more slender than families of low susceptibility. Increased stem lean was associated mostly with increased stem slenderness while elasticity was more influenced by pith diameter, stem density and wood radius.
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  • 49
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    Plant and soil 155-156 (1993), S. 391-394 
    ISSN: 1573-5036
    Keywords: Nitrogen ; rice ; simulation ; model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Yield potential of modern rice varieties and implications for N management were evaluated in a series of field studies that provided data for validation of an eco-physiological simulation model for rice. We tested the hypothesis that N was the major factor limiting yield potential of irrigated rice. The simulation model ORYZA1 was used to evaluate the observed yield differences between varieties grown with different N management and in different environments. The model explained differences in yield of the treatments resonably well on the basis of differences in radiation, temperature, leaf N content and variety coefficients for phenological development. It was demonstrated by the model and experimental data that yield levels of 6 t ha-1 in the wet season and 10 t ha-1 in the dry season can be obtained in the tropics with the current short duration varieties only when the N supply from soil and fertilizer is adequately maintained at key growth stages. Yield probabilities for rice crops were simulated for different environments using long term weather data at two Philippine sites.
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  • 50
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    Biology and fertility of soils 12 (1992), S. 241-252 
    ISSN: 1432-0789
    Keywords: Decomposition ; Litter ; Microarthropods ; Nitrogen ; 15N ; Litterbags ; Cornus florida ; Quercus prinus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Surface additions of (15NH4)2SO4 were used to measure the immobilization and subsequent movement of exogenous N added to two litter types of contrasting quality (Cornus florida and Quercus prinus). Litterbaskets were used to measure the litter mass loss and N dynamics and to follow the movement of the 15N label through litter, F layer, and soil pools. Half of the litterbaskets of each species were treated with naphthalene to reduce microarthropod densities. The faster decomposing C. florida litter maintained a higher excess atom % 15N, and a greater relative concentration of the labeled input (μg 15N g−1) than did Q. prinus litter. In both litter types the excess atom % 15N, relative concentration (μg 15N g−1), and absolute amount of label recovered in the litter declined over time. This occurred during a period of net accumulation of total litter N, implying simultaneous release of the initial input and immobilization of N from other sources. The concentration of 15N in the soil increased over time, while the F layer apparently acted as an intermediary in the transfer of 15N from litter to soil. Naphthalene effectively reduced microarthropod numbers in all horizons of the litterbaskets and significantly reduced the decay rates of Q. prinus, but not C. florida litter. Naphthalene did not appear to affect total N dynamics in the litter. However, with all horizons taken together, the naphthalene-treated litterbaskets retained more total 15N than the control litterbaskets. Naphthalene also changed the vertical distribution of 15N within litterbaskets, so that the litter retained less of the 15N-labeled input and the F layer and soil horizons retained more of the labeled input than in control litterbaskets. Our major conclusions are: (1) the N pool of decomposing litter is dynamic, with simultaneous N release and immobilization activating N turnover even during the net accumulation phase; (2) litter quality is an important determinant of immobilization and retention of exogenous N inputs and, therefore, turnover of the litter N pool; and (3) microarthropod activity can significantly affect the incorporation and retention of exogenous N inputs in decomposing litter, although these changes are apparently not reflected in net N accumulation or release during the 1st year of decomposition. However, the naphthalene may have affected microbially mediated N dynamics and this possibility needs to be considered in interpreting the results.
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  • 51
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    Biology and fertility of soils 14 (1992), S. 135-139 
    ISSN: 1432-0789
    Keywords: Nitrogen ; Mineralization ; Soil pretreatment ; Incubation experiment ; Freezing/thawing ; Long term field experiment ; Farmyard manure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary We studied the effects of pretreating soil samples (field-fresh, drying at 40° and 105°C, freezing/thawing) on N mineralization in an incubation experiment and on the dynamics of the organic N fraction extracted by K2SO4 solution. The soil samples were collected from plots in a long-term field experiment with the application of mineral fertilizer and farmyard manure. Compared with the field-fresh soil samples, freezing/thawing resulted in higher NO 3 − -N contents while the NH 4 + -N and the organic N content were increased by drying at 105°C. During the incubation period N mineralization was highest after the samples were dried at 105°C and a little lower in those dried at 40°C. After freezing/thawing the order of magnitude of N mineralization remained the same. The difference in organic N between the beginning and the end of the incubation experiment and the mineral N content at the end of the experiment were correlated significantly. Despite this correlation, however, the change in the organic N content underestimated the N mineralization rates.
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  • 52
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    Biology and fertility of soils 13 (1992), S. 92-95 
    ISSN: 1432-0789
    Keywords: Ammonia volatilization ; Grassland ; Nitrogen ; Soil enzymes ; Urea ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The volatilization of ammonia from simulated urine applied to small columns of soil was reduced by the presence of ryegrass growing in the soil. The ryegrass had been sown 18 weeks previously and had been cut on seven occasions to a height of 5–6 cm with the cut herbage removed. Cumulative volatilization over 8 days amounted to 39% of the urinary N from bare soil, and 23% in the presence of the ryegrass. In contrast, the volatilization of ammonia was increased by dead leaf litter placed on the soil surface, apparently due to the increase in surface area for urease activity and volatilization. Differences in the C:N ratio of the leaf litter over the range 13:1–29:1 had little effect on the extent of ammonia volatilization. When living ryegrass and dead leaf litter were examined together, the reduction in volatilization due to the ryegrass was the dominant effect.
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  • 53
    ISSN: 1432-2285
    Keywords: Nitrogen ; Photon flux density ; Growth ; Betula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Small birch plants (Betula pendula Roth.) were grown in a climate chamber at different, exponentially increasing rates of nitrogen supply and at different photon flux densities. This resulted in treatments with relative growth rate equal to the relative rate of increase in nitrogen supply and with different equilibrium values of plant nitrogen concentration. Nitrogen productivity (rate of dry matter increase per plant nitrogen) was largely independent of nitrogen supply and was greater at higher photon flux density. Leaf weight ratio, average specific leaf area (and thus leaf area ratio) were all greater at better nitrogen supply and at lower values of photon flux density. The dependencies were such that the ratio of total projected leaf area to plant nitrogen at a given photon flux density was similar at all rates of nitrogen supply. The ratio was greater at lower values of photon flux density. At a given value of photon flux density, net assimilation rate and net photosynthetic rate per shoot area (measured at the growth climate) were only slightly greater at better rates of nitrogen supply. Values were greater at higher photon flux densities. Acclimation of the total leaf area to plant nitrogen ratio and of net assimilation rate was such that nitrogen productivity was largely saturated with respect to photon flux density at values greater than 230 μmol m-2 s-1. At higher photon flux densities, any potential gain in nitrogen productivity associated with higher net assimilation rates was apparently offset by lower ratios of total leaf area to plant nitrogen.
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  • 54
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    Nutrient cycling in agroecosystems 32 (1992), S. 259-267 
    ISSN: 1573-0867
    Keywords: Nitrogen ; phosphorus ; timber increment ; fertilization ; Pinus radiata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two trials inPinus radiata growing on different sites in N.S.W. allowed consideration of fertilizer applications after 2nd or 3rd thinning. The trials included factorial applications of N and P at a single thinning intensity plus a further treatment which allowed assessment of different thinning intensities. The most significant growth responses were obtained by application of N and P in combination. The largest response (additional productivity compared with the unfertilized control) occurred 4 years after application and after 7 years there was no additional absolute response for either of the two sites. The largest fertilizer response was 70 m3 ha−1 over 7 years on one site and 36 m3 ha−1 on the other, indicating differences in absolute responses between sites. It was concluded that in planning treatments the most responsive sites near the end of the rotation should be selected to maximise economic returns. Foliage analyses indicated differences between sites at the commencement of the study. It was concluded that either a single year of foliage analyses at study commencement is of value, or sampling every year of the study should be used to analyse responses, but a single year of analysis during or at the end of the study would not be of value.
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    Biology and fertility of soils 12 (1991), S. 81-88 
    ISSN: 1432-0789
    Keywords: Fertilization experiment ; Soil organic matter ; Soil particle-size fractions ; Pyrolysis-field ionization mass spectrometry ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of more than 100 years of fertilization with farmyard manure on soil organic matter in comparison to unfertilized soil was studied in particle-size fractions using elemental (C and N) analyses and pyrolysis-field ionization mass spectrometry. Distinct differences in C and N concentrations and distribution and in the quality of organic matter between the size fractions and the fertilization treatments were observed. Clay-associated C and N were relatively higher in the unfertilized treatment, whereas the application of farmyard manure preferentially increased soil organic matter associated with the fine and medium silt fractions. Pyrolysis-field ionization mass spectrometry of soil fractions 〈20 μm showed increasing values for lignin monomers and dimers and fatty acids with larger equivalent diameters, whereas the proportion of N compounds, mono- and polysaccharides and phenolics decreased in the larger size fractions. Sand fractions were particularly rich in lignin fragments, mono- and polysaccharides, and alkanes/alkenes. These relationships seemed to be independent of management practices. In the same size fractions of the different treatments, however, a higher relative abundance of N-compounds, mono- and polysaccharides, phenolics, lignin monomers, and alkanes/alkenes was observed in the unfertilized variant. Lignin dimers and fatty acids were more abundant in the farmyard manure treatment. Both trends together imply that soil enrichment in organic matter due to the application of farmyard manure largely reflects an increase in lignin building blocks and partly reflects an increase in lipids such as fatty acids in the silt fractions. Therefore these constituents are of particular importance in assessing the positive effects of farmyard manure on soil fertility.
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    Biology and fertility of soils 10 (1991), S. 227-232 
    ISSN: 1432-0789
    Keywords: Carbon ; Nitrogen ; Cellulos ; N immobilization ; N mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The mass loss and N dynamics of barley stems and leaves, placed on the soil surface or buried, were examined over two summers. There was little difference in mass loss or N dynamics in straw placed 7.5 or 15 cm deep. However, the surface straw lost mass much more slowly and immobilized more N for a longer time than the buried straw. Filter paper had a slow rate of mass loss initially, but once started, lost mass much more rapidly than either the barley stems or leaves. Loss of mass was closely correlated with the cellulose loss in straw, whether buried or placed on the soil surface. The sustained rate of mass loss was 6.3 and 7.0% month-1, respectively, for surface and incorporated leaves compared with 3.5 and 4.3% month-1, for surface and incorporated stems. The greater loss sustained by the leaves was attributed to a lower lignin content rather than a higher N content, because the addition of N to the straw after 30 days in the field failed to increase CO2 evolution. Maximum net N immobilization occurred within 30 days for all the barley straw, except for the stems placed on the ground surface, which did not reach maximum N immobilization until the second summer. Immobilization and mineralization of N were estimated for a 3000 kg ha-1 grain crop. Surface straw immobilized 3.8 kg N ha-1 in the 1st year and 9 kg N ha-1 in the 2nd year, whereas incorporated straw immobilixed 3.5 kg N hs-1 in the 1st year and mineralized 4.5 kg N ha-1 in the 2nd year. Thus, in Alaska, residue management does not affect N fertilizer requirements in the 1st year, but an additional 13.5 kg N ha-1 is required for surface residues in the 2nd year.
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    Biology and fertility of soils 11 (1991), S. 279-284 
    ISSN: 1432-0789
    Keywords: Ammonia volatilization ; Nitrogen ; Soil enzymes ; Urea ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The proportion of the N that was volatilized as ammonia during 8 days, following the application of simulated livestock urine to soil, increased from 25 to 38% as the temperature of incubation was increased from 4° to 20°C in a system with a continuous flow of air at 70% relative humidity. However, volatilization was reduced if the application was followed by simulated rain; the reduction was greater as the amount of rain increased (up to at least 16 mm) and became less with an increasing length of time (up to 2–3 days) after the application of the urine. The effects of the soil water content before application of the urine, and of the relative humidity of the air, were generally small but volatilization was reduced by a combination of air-dry soil with a low relative humidity. Volatilization was slight (7%) when the flow of air was restricted to 0.5 h in every 12 h but, with an air flow for 12 h in every 24 h, the volatilization was much closer to that with a continuous flow for the whole 8-day period. When cool or dry conditions were imposed for 8 days and then more favourable conditions were instituted for a second period of 8 days, there was a substantial increase in volatilization following the change.
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  • 58
    ISSN: 1432-0789
    Keywords: Nitrogen ; urea ; crop residues ; particle-size fractionation ; ferrallitic soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The fate of N when incorporated in a ferrallitic soil was investigated during a 3-month incubation, using either 15N-labelled urea or 15N-labelled crop residues (sugarcane roots and leaves). The organic matter was characterized by particle-size fractionation. The urea-derived organic 15N was mainly found in the clay-sized fractions and was ascribed to biological activity. The plant-derived 15N was observed both in the sand-sized and in the clay-sized fractions; the former pool was ascribed to the persistence of crops residues, the latter to biological immobilization. The relative proportions of organic 15N recovered in the various clay fractions (coarse, fine, and very fine) were similar, irrespective of the nature of the added 15N. The very fine clay fraction (F〈0.05 μm) showed the highest isotopic excess, and thus gave rise to the highest turnover rate.
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    Biology and fertility of soils 11 (1991), S. 221-227 
    ISSN: 1432-0789
    Keywords: Straw ; Green manure ; Decomposition ; Particle size ; Soil ; Nitrogen ; Carbon mineralization ; CO2 evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A study was conducted to determine the effects of grinding, added N, and the absence of soil on C mineralization from agricultural plant residues with a high C:N ratio. The evolution of CO2 from ground and unground wheat straw, lentil straw, and lentil green manure, with C:N ratios of 80, 36, and 9, respectively, was determined over a period of 98 days. Treatments with added N were included with the wheat and lentil straw. Although the CO2 evolution was initially much faster from the lentil green manure than from the lentil or wheat straw, by 98 days similar amounts of CO2 had evolved from all residues incubated in soil with no added N. Incubation of plant residues in the absence of soil had little effect on CO2 evolution from the lentil green manure or lentil straw but strongly reduced CO2 evolution from the wheat straw. Grinding did not affect CO2 evolution from the lentil green manure but increased CO2 evolution from the lentil straw with no added N and from the wheat straw. The addition of N increased the rate of CO2 evolution from ground wheat straw between days 4 and 14 but not from unground wheat straw, and only slightly increased the rate of CO2 evolution from lentil straw during the initial decomposition. Over 98 days, the added N reduced the amounts of CO2 evolved from both lentil and wheat straw, due to reduced rates of CO2 evolution after ca. 17 days. The lack of an N response during the early stages of decomposition may be attributed to the low C:N ratio of the soluble straw component and to microbial adaptations to an N deficiency, while the inhibitory effect of N on CO2 evolution during the later stages of decomposition may be attributed to effects of high mineral N concentrations on lignocellulolytic microorganisms and enzymes.
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  • 60
    ISSN: 1573-0867
    Keywords: Nitrogen ; computer model ; organic matter turnover ; winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A computer model is described that simulates leaching, organic matter turnover and nitrogen uptake by a winter wheat crop. The model is assessed against a data set from the Netherlands where winter wheat was grown in two seasons (1982–3 and 1983–4) on three different soils in two different parts of the country. The model satisfactorily simulated the growth, N uptake and production of grain. It also simulated the dynamics of indigenous soil N well but it did not always account for the fate of applied fertilizer N. Some possible reasons for this and ways of improving the model are discussed.
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  • 61
    ISSN: 1573-0867
    Keywords: Nitrogen ; modelling ; management ; winter wheat ; soil ; crop
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A model that simulates changes in mineral N in the soil and N uptake by crops has been adapted to require as little detailed information as possible so that it is useful as an aid to management. The adapted model, which was developed in the UK, was tested against data from six experiments on winter wheat in the Netherlands. It proved reasonably successful in simulating the amounts of mineral N found in the soil in early spring and the changes that resulted from applying small amounts of fertilizer N in February. It was much less successful in simulating the effects of later, larger applications of N, mainly because the mineral N measured in the soil did not seem to respond to these applications. The uptake of N by the crops and their production of dry matter were simulated very well in some cases and rather less so in others.
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    Nutrient cycling in agroecosystems 29 (1991), S. 21-33 
    ISSN: 1573-0867
    Keywords: Nitrogen ; urea ; calcium ammonium nitrate ; cropping density ; N use efficiency ; slow release ; urease inhibitors ; West Africa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An overview is provided of the N efficiency research conducted within the West African Fertilizer Management and Evaluation Network (WAFMEN). Factors such as N rate, mode of N fertilizer application and choice of N sources for different agroecological zones of West Africa are discussed in relation to crop yield response. The interactive effects of cropping density and rainfall on N efficiency and yield are examined with particular emphasis on production of millet in Niger. The potential role of new, slow-release fertilizers as well as urea amended with urease inhibitors is mentioned in relation to present and future fertilizer N requirements in West Africa.
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    Biology and fertility of soils 10 (1990), S. 35-44 
    ISSN: 1432-0789
    Keywords: Pinus edulis ; Juniperus osteosperma ; Carbon ; Nitrogen ; Nitrification ; Microbial N ; N immobilization ; Fire ecology ; Nitrifying bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Forest floor litter, duff, and underlying soils were assembled in laboratory microcosms representing pinyon, juniper, and interspace field conditions. Burning removed more than 95% of both N and C from the litter, with losses from the duff dependent on soil moisture conditions. No significant changes in total N or C were noted in the soil. Immediate increases were observed in soil NH inf4 sup+ , decreasing with depth and related to soil heating. The greatest increases were noted in both the pinyon and juniper soils that were dry at the time of the burn, with interspace soils exhibiting the least changes. Soil NH inf4 sup+ closely approximated the controls on day 90 after the burns in all treatments. Ninety days after the burn microbial biomass N was highest in the controls, followed by the wet and then the dry-burned soils, in both the pinyon and juniper microcosms. This was inversely related to the levels of accumulated NO inf3 sup- . Nitrifying bacteria populations were indirectly correlated to soil temperatures during the burn. Population levels 90 days after the burn showed increases in both the wet- and the dry-burn treatments, with those in the pinyon treatments exceeding those found in the nitial controls of pinyon soils.
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    Biology and fertility of soils 9 (1990), S. 159-162 
    ISSN: 1432-0789
    Keywords: Soil animals ; Enchytraeidae ; Nitrogen ; Mineralization ; Soil moisture ; Temperature ; Cognettia sphagnetorum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of the enchytraeid species Cognettia sphagnetorum on N mineralization in homogenized mor humus was examined in a laboratory study. The mor humus was incubated in containers (150 ml) for 8 months at various temperatures and with different moisture levels. Two series were used, one with C. sphagnetorum and one without. The presence of enchytraeids in the cultures increased the level of NH4 + and NO3 - by about 18% compared with the cultures without enchytraeids. Almost 40% of this difference was explained by the decomposition of dead enchytraeids. Temperature and soil moisture were the most important factors controlling the mineralization rate. The optimum moisture for N mineralization was between pF 1.6 and 1.1.
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    Biology and fertility of soils 9 (1990), S. 1-13 
    ISSN: 1432-0789
    Keywords: Denitrification ; Flooded soil ; 15N ; Nitrogen ; Oryza sativa L. ; Wetland rice ; Urea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Although denitrification has long been considered a major loss mechanism for N fertilizer applied to lowland rice (Oryza sativa L.) soils, direct field measurements of denitrification losses from puddled rice soils in the tropics have only been made recently. This paper summarizes the results of direct measurement and indirect estimation of denitrification losses from puddled rice fields and reviews the status of research methodology for measurement of denitrification in rice fields. The direct recovery of (N2+N2O)-15N from 15N-enriched urea has recently been measured at sites in the Philippines, Thailand, and Indonesia. In all 12 studies, recoveries of (N2+N2O)-15N ranged from less than 0.1 to 2.2% of the applied N. Total gaseous N losses, estimated by the 15N-balance technique, were much greater, ranging from 10 to 56% of the applied urea-N. Denitrification was limited by the nitrate supply rather than by available C, as indicated by the values for water-soluble soil organic C, floodwater (nitrate+nitrite)-N, and evolved (N2+N2O)-15N from added nitrate. In the absence of runoff and leaching losses, the amount of (N2+N2O)-15N evolved from 15N-labeled nitrate was consistently less than the unrecovered 15N in 15N balances with labeled nitrate, which presumably represented total denitrification losses. This finding indicates that the measured recoveries of (N2+N2O)-15N had underestimated the denitrification losses from urea. Even with a probable two-or threefold underestimation, direct measurements of (N2+N2O)-15N failed to confirm the appreciable denitrification losses often estimated by the indirect difference method. This method, which determines denitrification losses by the difference between total 15N loss and determined ammonia loss, is prone to high variability. Measurements of nitrate disappearance and 15N-balance studies suggest that nitrification-denitrification occurs under alternate soil drying and wetting conditions both during the rice cropping period and between rice crops. Research is needed to determine the magnitude of denitrification losses when soils are flooded and puddled for production of rice.
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    Nutrient cycling in agroecosystems 26 (1990), S. 243-248 
    ISSN: 1573-0867
    Keywords: Nitrogen ; sulfur ; boron ; upland and lowland crops
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Asian agriculture has made enormous gains in food production despite rapid population growth and a shortage of land. This paper reviews the role of fertilizer in agricultural production and the results of recent research on fertilizers and plant nutrition in the region. Fertilizer use has contributed greatly to the increase in food production which has occurred largely in the high potential areas. In these areas research has shown that losses reduce the efficiency of broadcast urea and that the use of high analysis fertilizers is inducing sulfur deficiency in some areas. In upland areas, research has highlighted a major problem of boron deficiency in Thailand. Research progress is being made in understanding the magnitude of nitrogen fixation inputs and the role of shrub legumes in upland systems.
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    Nutrient cycling in agroecosystems 26 (1990), S. 89-98 
    ISSN: 1573-0867
    Keywords: Nitrogen ; phosphorus ; potassium ; sugarcane ; fertilizer use
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The amounts of N and K fertilizers used in the South African sugar industry have increased dramatically in the past four decades, due partly to an increase in the area under sugarcane but also to large increases in the amounts of N and K fertilizers applied per hectare. There has also been an increase in the amount of P fertilizer used but this has been more gradual. The main fertilizer carriers for cane and their relative efficiency are discussed. During this period there has been considerable research into the nutrient requirements of sugarcane. Correlations established between soil and leaf analysis and crop responses to N, P and K fertilizers, and their effects on cane quality, are reviewed. While fertilizer recommendations based on soil and leaf analysis have provided a useful guide for determining the nutrient requirements of cane, they are continually being modified in the light of current research.
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    Nutrient cycling in agroecosystems 26 (1990), S. 253-269 
    ISSN: 1573-0867
    Keywords: Nitrogen ; phosphorus ; sulphur ; nutrient balances ; surface waters ; North Sea ; Baltic Sea ; eutrophication ; hypertrophication ; primary production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Dissolved inorganic nitrogen and phosphorus, their relationship to each other (DIN/DIP) as predisposing (nutrient) factors, as well as prevailing weather as a triggering factor all work together to induce the primary production and hence the eutrophication (hypertrophication) process in surface waters. Sulfate likewise is a decisive predisposing factor influencing the eutrophication process by reducing N availability but increasing P availability and thus acting towards an N limitation of the primary production. This is one of the reasons why marine (coastal) waters and estuaries often exhibit N limitation with respect to primary production, while freshwater ecosystems often tend to exhibit P limitation. Within the N and P balance of agriculture of some countries of Western Europe (Netherlands, Denmark, Switzerland, FRG, UK and Sweden for N, resp. Netherlands, FRG and GDR for P) more the level than the efficiency of the N and P applications indicates the extent of the nutrient surplus. Despite 59–73% N utilization in plant production, the rate of 13–23% for agriculture as a whole equals to the 12–21% efficiency of N use in animal production. The varying N surplus in agriculture in the separate countries of 124 to 465 kg N ha−1 a−1 is determined almost exclusively by the level of the N application and not by its efficiency. The situation is similar for P: In spite of P utilization in plant production of 59–76%, P utilization in total agriculture is only 11–38%, or comparable to the P efficiency within animal production of 10–34%. The differing P excess balance of 55 to 88 kg P2O5 ha−1 a−1 is influenced by the level of the P application. The N and P efficacy of total agriculture hence is determined almost completely by that of animal production, since 83–95% (N basis) and 76–94% (P basis) of the total plant production (on top of the nationally varying levels of N and P use via imported feeds) are fed to animals — with the low N and P utilization cited above. Agriculture's share of the N and P emissions into surface water of several countries/regions in Western Europe (FRG, Netherlands, Italy, Denmark, Switzerland, Norway) ranges from 37 to 82% resp. 27 to 38%. Its share in the flus into the North Sea catchment basin will be about 60% for N and 25% for P related only to the anthropogenic material carried by the rivers. Agriculture's share in the atmospheric N emissions into the North and Baltic Seas can be estimated at about 65% or 55%, resp. while the remaining approx. 35% or 45%, resp. are traceable primarily to anthropogenic burning processes. For agriculture the priority lies in limiting N emissions into surface water caused by leaching, erosion and NH3 emissions, and reducing P emissions mainly through soil conservation (protection against erosion) and water protection. As regards N this means a demand for comprehensive protection of groundwater and atmosphere differentiated according to the potential for losses or the risk of losses on a site, also outside the protection zones. As regards P only those areas can be included in the demand for reduction of emissions that are actually threatened by erosion or surface runoff. Plenty of short-term and long-term measures are available to agriculture to reduce N and P emissions. Especially the long-range measures (such as creating nutrient balances on farms and fields, the integration of animal and plant production, maintaining maximum livestock densities according to the ability of areas to absorb nutrients, altered feeding programs in animal nutrition, changes in livestock keeping (slurry→deep litter), increasing the internal and external recycling of N and P) are capable of bringing about a satisfactory degree of success within the next 20 to 30 years.
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    Biology and fertility of soils 8 (1989), S. 189-190 
    ISSN: 1432-0789
    Keywords: Nitrogen ; Ammonium ; Nitrate ; Nitrogen extraction ; Soils ; Nitrogen mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A roller bed and rotary end-over-end shaker were compared for the extraction of mineral N from a variety of soil types; both were equally efficient with an optimum extraction time of 30 min. However, the roller bed permitted a greater operational capacity, a faster throughput of samples, and easier identification of sample bottles compared with the end-over-end shaker. More NH4 +-N and NO3 −-N (P〈0.001) was recovered from soil by 2 M KCl than by any other extractant, in a soil: extractant ratio of 1 to 5 (w:v), except water, which was equally efficient at removing NO3 −-N from soils.
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    Biology and fertility of soils 8 (1989), S. 13-18 
    ISSN: 1432-0789
    Keywords: Bacteria ; Protozoa ; Predation ; Nitrogen ; Mineralization ; Plant uptake ; Soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Microbial N from 15N-labelled bacterial biomass was investigated in a microcosm experiment, in order to determine its availability to wheat plants. Sterilized soil was inoculated with either bacteria (Pseudomonas aeruginosa alone or with a suspension of a natural bacterial population from the soil) or bacteria and protozoa to examine the impact of protozoa. Plant biomass, plant N, soil inorganic N and bacterial and protozoan numbers were determined after 14 and 35 days of incubation. The protozoa reduced bacterial numbers in soil by a factor of 8, and higher contents of soil inorganic N were found in their presence. Plant uptake of N increased by 20010 in the presence of protozoa. Even though the total plant biomass production was not affected, the shoot: root ratios increased in the presence of protozoa, which is considered to indicate an improved plant nutrient supply. The presence of protozoa resulted in a 65010 increase in mineralization and uptake of bacterial 15N by plants. This effect was more pronounced than the protozoan effect on N derived from soil organic matter. It is concluded that grazing by protozoa strongly stimulates the mineralization and turnover of bacterial N. The mineralization of soil organic N was also shown to be promoted by protozoa.
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    Agroforestry systems 8 (1989), S. 257-265 
    ISSN: 1572-9680
    Keywords: Nitrogen ; phosphorus ; potassium ; rooting density ; root biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient competition between interplanted species is investigated using mechanistic modelling. Though tree and crop plant roots may occupy the same soil volume, nutrient competition is seen to be dependent on soil supply mechanisms. Model simulations illustrate the effects of nutrient diffusion rate, mobility/soil interaction, root diameter, soil moisture content, and rooting density on nutrient concentration gradients governing uptake adjacent to plant roots. These factors, unique for each nutrient and soil, combine to determine the potential for competition in agroforestry plantings. Nutrient competition is most likely for the more mobile nutrients and mechanistic modelling can be used to select tree and crop species with superior rooting and physiological characteristics for interplantings to better manage below-ground competition.
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    Nutrient cycling in agroecosystems 20 (1989), S. 11-15 
    ISSN: 1573-0867
    Keywords: Nitrogen ; nitrogen isotopes ; fertilizers ; 15N balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Calculations in nitrogen (N) balance research using15N involve several steps that require care to avoid errors. The objective of this paper is to provide examples of these calculations using established procedures and to present shortened alternative calculations that give the same result. The calculations examined include determination of the amount of N to apply, determination of the atom %15N abundance needed in the labeled fertilizer, preparation of the labeled fertilizer, and calculation of the fertilizer N recovered. Calculations needed in the preparation of the labeled fertilizer using established procedures include the determination of the mean atomic weight of the enriched source from which the labeled fertilizer is prepared. This determination is not needed in the shortened alternative calculations, because the procedure places the calculations on a mole basis rather than a mass basis.
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    Biology and fertility of soils 6 (1988), S. 22-25 
    ISSN: 1432-0789
    Keywords: Nitrogen ; Green manure ; Sesbania sp. ; Wetland rice ; Oryza sativa L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two annual species of Sesbania, S. aculeata and Sesbania sp. PL Se-17, were field evaluated as green manure for wetland rice in an alkaline soil. The two species were raised as a catch crop during summer in a wheat-rice rotation, and added as 24.7 and 20.8 t ha−1 of green matter, 116 and 98 kg N ha−1, respectively, after 45 days of growth. For the optimum green manuring effect on rice grain yield and N uptake, S. aculeata required 5 days of decomposition (after turning in and before rice transplantation), whereas no decomposition period was necessary for Sesbania sp. PL Se-17. The effect on grain yield and N uptake of rice was equivalent to an application of 122 and 78 kg ha−1 of chemical N, for the two species, respectively. There was no residual effect of the green manuring on the soil N status after rice harvest.
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    Plant and soil 105 (1988), S. 149-152 
    ISSN: 1573-5036
    Keywords: C release ; liming ; mesh bag ; Nitrogen ; N release ; red clover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Red clover root material confined in mesh bags was buried in three different limed and unlimed soils and incubated for 196 days at room temperature. Remaining amounts of organic matter, as well as concentrations of C and N of the decomposing material were determined three times during the incubation and finally the concentration of soil mineral N and pH of remaining roots was also assessed. Liming only temporarily affected the decomposition rate of organic matter and N release, and at the end of the incubation no effects could be observed due to liming. A possible explanation is that the decomposing root residues provide a well buffered micro-environment for the decomposing microflora. Liming did not change the pH of the root residues even when 97–98% of dry mass had disappeared from the mesh bags. Concentrations of mineral N were higher in limed than in unlimed soils.
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  • 75
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    Nutrient cycling in agroecosystems 16 (1988), S. 273-284 
    ISSN: 1573-0867
    Keywords: Nitrogen ; coated fertilizer ; slow-release fertilizer ; RLCU
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An experimental fertilizer called reactive layer coated urea (RLCU) has been developed by coating urea with a mixture of diisocyanate and polyol in the presence of a catalyst. The hard, durable layer that is formed on the granule conveys slow-release character to the product. A series of soil incubation tests were conducted under simulated upland conditions for periods up to 56 days to study the effect of factors such as temperature, pH, soil moisture, and organic C additions on N release. The N release rate from RLCU was shown to be increased with increasing temperature and decreasing coating thickness. It was unaffected by the addition of lime to raise the pH or organic carbon sources to increase microbial activity. Although a slight effect of soil moisture was noted, it was not pronounced. Urea release tended to be in two stages — a constant diffusive stage in which, it is postulated, urea was still dissolving within the granule and diffusing to the soil at a constant rate and a slower logarithmic stage where the rate of release decreased with time.
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  • 76
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    Nutrient cycling in agroecosystems 17 (1988), S. 101-118 
    ISSN: 1573-0867
    Keywords: Nitrogen ; phosphorus ; potassium ; organic matter ; fallow ; forecasting ; fertilizer requirement ; Sierra Leone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The quantities of nitrogen, phosphorus and potassium supplied by an ‘average’ African soil cleared from bush fallow, assuming no losses, were approximated. Values ranged from 23 to 120 Kg N ha−1, 1.8 to 12 Kg P ha−1, 47 to 187 Kg K ha−1, depending on type of fallow, length of fallow, drainage and extent of depletion of native supplies. Additional amounts of 4 to 5 Kg N ha−1, 4 to 6 Kg P ha−1 and 14 to 20 Kg K ha−1 are obtained from the ash. Using crop nutrient removal data and approximate efficiencies of native and fertilizer N, P and K, fertilizer requirements at the reconnaissance level were estimated for selected target yields. For newly cleared uplands at cropping/fallow ratio of 2:7, N fertilizer requirements for cassava (30 t ha−1), maize (4 t ha−1), and sweet potato (16 t ha−1), were 138, 98, 42 kg ha−1 respectively. Wetland rice (4 t ha−1) required 55 kg N ha−1. Corresponding P fertilizer requirements for cassava, maize, sweet potato, upland rice (1.5 t ha−1) and ground-nut (1 t ha−1) were 190, 80, 30, 30 and 16 kg P ha−1 respectively. Wetland rice required 83 kg P ha−1. Substantial residual values of applied P are to be expected. Cassava required 60 kg ha−1 of K on newly cleared land. In soils of lowered nutrient status higher N, P, and K fertilizer requirements were indicated for all crops. Land use data from Sierra Leone were used to illustrate how the total quantities of N, P and K fertilizers in a country in the forest zone of Africa can be approximated. Fertilizer needs in Sierra Leone were in decreasing order P 〉 N ≫ K. N, P and K requirements were estimated to be 10,000 t, 20,000 t and 4,000 t respectively. The nutrient balance sheet method described in this paper is a useful tool to estimate the order of magnitude of fertilizer requirement at selected target yields for countries in Africa.
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  • 77
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    Biology and fertility of soils 5 (1987), S. 230-234 
    ISSN: 1432-0789
    Keywords: Earthworm casts ; Microbial respiration ; Microbial biomass ; Nitrogen ; Phosphorus ; Aporrectodea caliginosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Microbial respiration, microbial biomass and nutrient requirements of the microflora (C, N, P) were studied in the food substrate (soil taken from the upper 3 cm of the mineral soil of a beech wood on limestone), the burrow walls and the casts of the earthworm Aporrectodea caliginosa (Savigny). The passage of the soil through the gut caused an increase in soil microbial respiration of about 90% over a 4-week period. Microbial biomass was increased only in freshly deposited casts and decreased in aging faeces to a level about 10% lower than in soil. Microbial respiration of the burrow walls was only increased over a shorter period (about 2 weeks). The microflora of the soil and the burrow walls was limited by P, whereas in earthworm casts, microbial growth was limited by the amount of available C. In aging faeces the P requirement of the microflora increased and approached that of the soil. Immobilization of phosphate in earthworm casts is probably caused by mainly abiotic processes. C mineralization by soil microflora fertilized with glucose and P was limited by N, except in freshly deposited casts. Ammonium, not nitrate, was responsible for this process. N dynamics in earthworm casts are discussed.
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  • 78
    ISSN: 1432-0789
    Keywords: Microbial biomass ; Tillage ; Rotation ; Carbon ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three mollisols, typical of the Palouse winter wheat region of eastern Washington and northern Idaho, were analyzed for microbial biomass, total C and total N after 10 years of combined tillage and rotation treatments. Treatments included till, no-till and three different cereal-legume rotations. All crop phases in each rotation were sampled in the same year. Microbial biomass was monitored from April to October, using a respiratory-response method. Microbial biomass, total C and total N were highest under no-till surface soils (0–5 cm), with minimal differences for tillage or depth below 5 cm. Microbial biomass differences among rotations were not large, owing to the relative homogeneity of the treatments. A rotation with two legume crops had the highest total C and N. Microbial biomass was significantly higher in no-till surface soils where the current crop had been preceded by a high-residue crop. The opposite was true for the tilled plots. There was little change in microbial biomass over the seasons until October, when fresh crop residues and rains had a strong stimulatory effect. The seasonal pattern of biomass in no-till surface soils reflected the dry summer/winter rainfall climate of the region. The results of this study show that numerous factors affect soil microbial biomass and that cropping history and seasonal changes must be taken into account when microbial biomass data are compared.
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  • 79
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    Plant and soil 100 (1987), S. 47-69 
    ISSN: 1573-5036
    Keywords: Ammonia volatilization ; Denitrification ; Nitrogen ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Inappropriate method and timing of N fertilizer application was found to result in 50–60% N losses. Recent nitrogen transformation studies indicate that NH3 volatilization in lowland rice soils is an important loss mechanism, causing a 5–47% loss of applied fertilizer under field conditions. Estimated denitrification losses were between 28 and 33%. Ammonia volatilization losses from lowland rice can be controlled by i) placement of fertilizer in the reduced layer and proper timing of application, ii) using phenylphosphorodiamidate (PPD) to delay urease activity in flooded soils, and iii) using algicides to help stabilize changes in floodwater pH. Appropriate fertilizer placement and timing is probably the most effective technique in controlling denitrification at the farm level. The effectivity of nitrification inhibitors as another method is still being evaluated. With 60–80% of N absorbed by the crop derived from the native N pool, substantial yield gains in lowland rice are highly possible with resources already in the land. Extensive studies on soil N and its management, and an understanding of soil N dynamics will greatly facilitate the decrease in immobilization and ammonium fixation in the soil and the increase in N availability to the rice crop. Critical research needs include greater emphasis on N transformation processes in rainfed lowland rice which is grown under more harsh and variable environmental regimes than irrigated lowland rice.
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  • 80
    ISSN: 1573-5036
    Keywords: Ammonium ; Clover ; Manganese ; Nitrate ; Nitrogen ; Symbiotic ; Tolerance ; Toxicity ; Trifolium subterraneum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A wide range of clover accessions were screened for reaction to manganese (Mn) in solution culture. Growth was supported with ammonium nitrate (NH4NO3) or symbiotic nitrogen to assess Mn effects on symbiosis and the suitability of NH4NO3 dependent growth for assessing Mn tolerance in clover. Reduction of dry matter at Mn 45 ppm varied 0–70%, at Mn 90 ppm, 38–92%, the extent depending on genotype. Tolerant clovers tended to restrict the movement of Mn from roots to shoots. Several previously untested lines were the most tolerant while some commercial lines possessed poor tolerance. Ranks of tolerance for the two nitrogen (N) sources at Mn 45 ppm were correlated suggesting no dominant, discriminatory effects of N source on Mn tolerance; but inclusion of symbiotic effectiveness in a multiple correlation improved the relation between relative tolerances of genotypes under different N sources. Mn affected some aspects of symbiosis. Total nodule nitrogenase activity mainly reflected effects of Mn on nodule number but nitrogenase activity per nodule also contributed. To establish relative tolerances of subterranean clover to Mn growth with NH4NO3 is suitable and useful when symbiotic effectiveness is unknown.
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  • 81
    ISSN: 1573-5036
    Keywords: Denitrification ; Leaching ; Legumes ; Nitrification ; Nitrogen ; Tillage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen (N) dynamics were studied in conventional and no-tillage agroecosystems on the Georgia Piedmont. Nitrogen inputs in the form of ammonium nitrate (95 kg-N/ha) and winter legume (crimson clover) residues were compared. The legume provided adequate N for summer crop (grain sorghum) production, but water use by the legume reduced the ability of sorghum to utilize the N. Legume N inputs became availabe to plants more gradually than fertilizer inputs. Weed growth and potential denitrification activity were higher in legume-N treatments than in fertilizer-N treatments. Tillage affected the timing of N avaialbility more than the total amount of available N. Summer crops took up more N under conventional tillage while winter crops took up more N under no-tillage. Denitrification activity was higher under no-tillage but was not a significant output from the agroecosystems. Leaching losses of N differed seasonally between treatments but were not significant in any of the agroecosystems.
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  • 82
    ISSN: 1573-5036
    Keywords: Cucumber ; Nitrogen ; Root death
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The nitrogen concentration of the nutrient solution was reduced for a short period, in order to get a bigger root mass and less root death than normal. Root death was reduced but not prevented by manipulating the nitrogen concentration. There seemed to be a connection between root death and the time of the first harvest.
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  • 83
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    Biology and fertility of soils 2 (1986), S. 109-112 
    ISSN: 1432-0789
    Keywords: Straw ; Phytotoxins ; Acetic Acid ; Wheat ; Barley ; Cultivar ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Acetic acid production over 10 days from fresh barley straw was greater than that from fresh wheat straw, but there were only minor consistent differences between different cultivars. The effect depended on the soil type on which the straw had been produced and acid production was greatest with the largest amounts of N fertilizer which had been used. The fertilizer also affected the C:N ratio of the straw
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  • 84
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    Plant and soil 96 (1986), S. 149-151 
    ISSN: 1573-5036
    Keywords: Denitrification ; Nitrogen ; Poa pratensis ; Soil moisture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Denitrifer populations of a silt and silt loam soil under a Kentucky bluegrass turf were enumerated using the most probable number (MPN) procedure. The influence of soil texture, soil depth, soil moisture, and additions of nitrate fertilizer on denitrifier populations were determined. Saturated soil conditions increased denitrifier populations 87-fold in the silt soil and 121-fold in the silt loam soil. Denitrifier populations did not differ significantly between soil depths and additions of fertilizer nitrate did not influence populations.
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  • 85
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    Plant and soil 96 (1986), S. 185-196 
    ISSN: 1573-5036
    Keywords: Carbon ; Carbon accumulation ; Carbon cycle C/N ; Degradation recovery ; Land use ; Nitrogen ; Subtropical forest ; Subtropical pastures ; Subtropical soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The assumption that the organic matter content of tropical forest soils is oxidized to atmospheric carbon dioxide when these soils are converted to agricultural use was tested using results of soil surveys in Puerto Rico (1940's, 1960's, and 1980's). Results showed that under intensive agricultural use, soil carbon in the top 18 cm of soil was about 30–37 Mg/ha, regardless of climatic conditions. Reduced intensity of agricultural use resulted in an increase of soil carbon in the order of 0.3–0.5 Mg.ha−1. yr−1 over a 40-yr period. Rates of soil carbon accumulation were inversely related to the sand content of soils. The relation between rates of soil carbon accumulation and climate or soil texture were better defined at higher soil carbon content. Soils under pasture accumulated soil carbon and often contained similar or greater amounts than adjacent mature forest soils (60–150 Mg/ha in the top 25 or 50 cm). Soils in moist climates exhibited greater variations in soil carbon content with changes in land use (both in terms of loss and recovery) than did soils in dry climates. However, in all life zones studied, the recovery of soil carbon after abandonment of agriculture was faster than generally assumed. Low carbon-to-nitrogen ratios suggested that intensively used soils may be stable in their nutrient retention capacity. The observed resiliency of these soils suggested that their role as atmospheric carbon sources has been overestimated, while their potential role as atmospheric carbon sinks has been underestimated.
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  • 86
    ISSN: 1573-5036
    Keywords: Zea mays L. ; Nitrogen ; Protein ; Roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary When roots of five day-old maize seedlings were exposed to15N-nitrate, a constant (25–29%) proportion of the reduced15N derived from the entering15N-nitrate accumulated as insoluble15N nitrogen. Constancy was established by two hours and lasted through 12 hours at ambient15N-nitrate concentrations of 0.05 mM to 20.0 mM. Even when little15N nitrate had been reduced (〈2 μmoles), there was a linear relationship between accumulation of insoluble15N (but not accumulation or translocation of soluble reduced15N) and total reduced15N. It is proposed that protein synthesis from the entering nitrate occurs in close association with nitrate reduction.
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  • 87
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    Plant and soil 95 (1986), S. 191-200 
    ISSN: 1573-5036
    Keywords: Atmospheric input ; Douglas fir Fertilization ; Foliar analysis ; Forest nutrition ; N/P ratio ; Nitrogen ; Nutrient status ; Phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A re-examination of earlier NPK fertilization experiments in Douglas fir stands on sandy soils shows the effects of high nitrogen input by air pollution during the last 10–15 years on plant nutrition at these sites. In 1960, experimental plots showed a positive growth reaction to nitrogen, phosphorus, and potassium fertilization. All suffered from severe phosphorus deficiency in 1984, low phosphorus in the needles was invariably accompanied by a high nitrogen content, with all N/P ratios between 20 and 30. The same conclusion emerges from an independent investigation of nutrient status of a selection of Douglas fir stands. Hence, if stand productivity and a balanced nutrient status of the trees is to be maintained, the increase in atmospheric input of nitrogen calls for supplementary fertilization. Given the current N/P ratios in the needles, a positive growth response to phosphorus fertilization is to be expected.
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  • 88
    ISSN: 1573-5036
    Keywords: Alfalfa ; Barley ; Corn ; Management ; Nitrogen ; Nitrogen fixation ; Plow down ; Red clover ; Sweetclover ; Temperate climate ; Trefoil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Under some conditions the plow down of forage legumes increases the yield of subsequent crops, which is usually caused by improved soil N. However, better soil structure is also a contributing factor. Three experiments were conducted to measure the effect of legume plow down on the yield of subsequent corn crops grown at the Ottawa Research Station (ORS), Ottawa, Canada. In all experiments, corn yields were not affected by legume species, legume cultivars, and/or planting methods. Corn yields from barley plots receiving 0, 60, or 120 kg N ha−1 did not differ until two years after establishment in one experiment and three years in another. The data from these experiments indicated that soil N was high at the ORS, which may inhibit N2-fixation by forage legumès in the establishment year. Therefore, legume plow down was not beneficial to subsequent crops under these conditions. Two other experiments were conducted to measure the effect of legume plow down on the yield of subsequent barley crops. In both experiments, barley yields in the field were not affected by legume type or legume seeding density. Greenhouse and field data indicated that the two cuts with removal strategy benefitted the most to succeeding crops. Data from the greenhouse test indicated that soil N levels were not low in the establishment year, and that some cultivars improved soil fertility more than others.
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  • 89
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    Plant and soil 91 (1986), S. 353-356 
    ISSN: 1573-5036
    Keywords: Hondeum vulgare L. ; Nitrogen ; NO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Exposure of the leaves of young barley plants to nitrogen dioxide (NO2) was shown to affect the rate of translocation of N, the form in which it is transported in the xylem stream and the partitioning of N between roots and shoots. Following its entry through the leaves, NO2 is assimilated by the plant into reduced nitrogenous compounds which accounted for the major increases in plant N content and growth. The various effects of atmospheric NO2 upon barley seedlings were strongly influenced by nitrate supply to the roots.
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  • 90
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    Plant and soil 93 (1986), S. 347-357 
    ISSN: 1573-5036
    Keywords: Dew ; Grasslands ; Nitrification ; Nitrogen ; Semiarid ecosystems ; Soil texture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The depth distributions of rates of net nitrogen mineralization and nitrification were measured in a series of field and laboratory incubations. Field studies suggested that the highest rates of mineralization and nitrification occurred in the surface 2.5 cm such that forty to sixty percent of the N mineralization in 20-cm soil column occurred in the surface 2.5cm. Some upward nitrate movement occurred but laboratory studies suggested that surface rates were not an artifact of nitrate mobility alone. Microclimatic data indicate that either dew or upward movement and condensation of soil water vapor may drive biological activity at the soil surface. High rates of N mineralization even in dry horizons were sustained as long as water was stored within the 0-to 20-cm depth. High rates of nitrification were found in all incubations, and field measurements showed NO 3 − to be the predominant form of inorganic N, despite previous characterization of the shortgrass steppe as an NH 4 + -dominated system.
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  • 91
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    Plant and soil 93 (1986), S. 373-382 
    ISSN: 1573-5036
    Keywords: Calcium ; Fertilizer ; Magnesium ; Nitrogen ; Nutrient content ; Phosphorus ; Pinus radiata ; Potassium ; Superphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nutrient contents of aPinus radiata stand, that is, aboveground tree, understorey, forest floor and soil to 200 mm depth, were estimated in a replicated fertilizer trial, treated 30 years previously. The fertilizer treatments were 0, 25, 50, 75 and 100 kg P/ha as broadcast superphosphate. Highly significant growth responses had been obtained to the applied P. Estimation of the P content of the stand showed that 129%, 89%, 72% and 67% of the applied P was found in the 25, 50, 75 and 100 kg P/ha treatments respectively. The larger losses of P at the higher application rates would explain the lack of increased response with the highest application rate, however, it also shows that significant quantities of P are still present after a period of 30 years, giving a basis for growth responses in the subsequent rotations. Elevated quantities of N, Ca, Mg and K were found in the treatments compared with the control and these could not be explained on the basis of atmospheric inputs. For the cations, uptake from deeper in the soil profile could explain most of the effect but not for the higher amounts of N which, in the case of the highest superphosphate treatment, amounted to an accumulation of 27 kg N/ha/yr. These nutrient changes together with increased soil organic matter contents are considered to have provided a long term increase to the site productivity.
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  • 92
    ISSN: 1573-5036
    Keywords: Fertilizer ; Lupinus ; Nitrogen ; Nitrogen fixation ; Nutrient availability ; Pinus ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects ofLupinus angustifolius, L. arboreus. and nitrogen fertilizer plus weedicide on soil inorganic nitrogen, and the growth, nutrition and water status ofPinus radiata seedlings were compared on a sandy podzol in Victoria Australia. Both lupins increased the concentration of soil inorganic nitrogen from 6 μg g−1 to at least 11 μg g−1 one year after treatment.Lupinus arboreus (a perennial) led to high mortality ofP. radiata seedlings and no growth response in survivors because it competed for water during summer. In contrast,L. angustifolius (an annual) senesced prior to summer and resulted in increased fascicle size and stem growth rates ofP. radiata. Growth ofP. radiata withL. angustifolius was similar to that with weedicide only. The concentration. of phosphorus in foliage ofP. radiata seedlings was highest when growth withL. angustifolius. However, the highest growth rate ofP. radiata occurred in the nitrogen fertilizer plus weedicide treatment.
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  • 93
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    Plant and soil 94 (1986), S. 147-151 
    ISSN: 1573-5036
    Keywords: Nitrogen fixation ; 15N Rhizobia ; Vigna radiata ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Remobilization of15N from vegetative tissue of mungbean (Vigna radiata (L.) Wilczek) into pods was measured during the reproductive phase of growth. Plant tissue was labelled with15N during vegetative development. Experiments were conducted in the field at two sites. At one site the soil provided cowpeas with most of their N but at the other site N fixation provided most of the N. Remobilized N from vegetative tissue to pods occurred soon after they began to develop. The quantity of the labelled N ultimately remobilized to the pods amounted to 50% for one cultivar (Tx33) at the high soil N site and 70% at the low N site. For the other cultivar (Tx13) the values were 25% and 30%, respectively. The two cultivars performed very differently with respect to partitioning of N into pods and the rate of N fixation. Even though more N was accumulated in the shoots of the high N fixing cultivar (Tx13) less total N was contained in the pods.
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  • 94
    ISSN: 1573-5036
    Keywords: Betula ; Clones ; Growth responses ; Nitrogen ; Salix ; Solution culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Growth of selected clones of birch and willow obtained from nitrogen deficient soils was compared with that of unselected controls in pot experiments using three levels of nitrogen. Unselected controls of both genera continued shoot growth, albeit very slowly, with a very low level of nitrogen (5 ppm), while selected clones of birch grew significantly more than the controls. Selected clones of willow, on the other hand, ceased shoot growth after 10 weeks with this low nitrogen treatment. Nevertheless, they remained healthy, their leaves containing similar concentrations of nitrogen to those of the plants which continued stem growth throughout the experiment. Furthermore, they had very high root: shoot ratios compared with those of control willows and both selected and unselected birch. The two genera may have developed different mechanisms for tolerating low nitrogen, birch producing a small, relatively efficient root system; willow a larger but less efficient one. Both appear equally effective in ensuring survival on low-nitrogen sites in the field since all the selected clones were obtained from such sites and have survived well in field trials on similar sites. Both birch and willow responded toincreased nitrogen availability with increasing shoot growth and a relative decline in root growth. However, whereas in willow the unselected plants responded significantly more than selected clones, a similar but less markeddifference was found in birch. It appears that in both genera, as in herbaceous plants originating from nitrogen deficient sites, selected clones are less able to respond to increasing nitrogen supply than control plants from more fertile habitats. Attempts to correlate the response of the selected clones to nitrogen in this experiment with that to added nitrogen fertilizer in field trials has been unsuccessful. Further work is required to determine the importance of the many interacting factors which influence the response of young trees to nitrogen under the unusual field conditions associated with restored mineral workings.
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  • 95
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    Plant and soil 92 (1986), S. 319-339 
    ISSN: 1573-5036
    Keywords: Eucalypt forests ; Litterfall ; Nitrogen ; Nutrient cycling ; Turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nutrient pools in litter and soil and the major nutrient transfers and additions in rainfall, throughfall and litterfall were measured in eight mature, undisturbed eucalypt forests covering a range of species, climate, productivity and soil type. Litterfall is the major pathway for the return of N, P, Ca and usually Mg, to the soil. The forests covered almost the range of litterfall reported for eucalypt forests and, in conjunction with published data, litterfall was strongly related to climatic variables. Extractable P in the soil and P concentrations in litter and litterfall were significantly higher in two sub-alpine forests (Eucalyptus pauciflora andE. delegatensis) than in all other forests. In general, nutrient turnover, particularly N turnover, was related to the rate of organic matter turnover. Rates of organic matter turnover in these forests and in other studies of eucalypts were correlated with climatic conditions using the simple climatic scalar developed by Vitousek. Nitrogen turnover, especially that proportion cycling via leaf litterfall is primarily a function of organic matter turnover, but litter quality appears also to have an influence.
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  • 96
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    Plant and soil 92 (1986), S. 427-430 
    ISSN: 1573-5036
    Keywords: Light ; Nitrogen ; Fixation ; Nodulation ; Phytochrome ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Rooted leaves and plants were irradiated at the end of the photoperiod with red light for 15 minutes, while another group was also irradiated with red light and immediately afterwards with far- red light. The reduction in Pfr/Ptotal established by far red irradiation promoted nodulation probably by affecting an hormonal balance.
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  • 97
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    Plant and soil 86 (1985), S. 27-34 
    ISSN: 1573-5036
    Keywords: Loblolly pine ; Nitrogen ; Nutrient ratios ; Phosphorus ; Pinus taeda
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen and phosphorus limitations to growth are common in many loblolly pine (Pinus taeda) stands. Interactions of these nutrients may complicate interpretation of foliar nutrient analysis for predicting response to forest fertilization. Proportions of foliar nutrient concentrations (and the changes in these proportions following fertilization) were examined in 36 semi-mature loblolly pine plantations in the southeastern United States. Mean proportions of nutrient concentrations (N∶P∶K∶Ca∶Mg) for non-fertilized stands were 100∶9.3∶36.5∶17.2∶9.2. Potassium and phosphorus were higher. Nitrogen fertilization generally decreased the P∶N ratio and enhanced growth, indicating a nitrogen deficiency in most stands under study. Additions of nitrogen and phosphorus together yielded a significant increase in the P∶N ratio. Effects of fertilization effects on other nutrient concentration ratios were also examined.
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  • 98
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 86 (1985), S. 101-112 
    ISSN: 1573-5036
    Keywords: Alfalfa ; Assimilation ; Carbon ; Corn leaf ; Dissimilation ; Glucose ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The stoichiometry of soil biomass synthesis was studied with glucose, glucose+N, alfalfa and corn leaf amended soil. Equations describing the quantitative relationship found for the dissimilation of substrate C and related oxidative assimilation of C by the biomass were developed. The analytical approach involved measurement of soluble C consumed by persulfate oxidation (POC). Carbon flow patterns showed that the observed decrease in POC correlated well with an increase in cell C (0–44 h). With glucose alone 47% of the initial POC was consumed and with glucose+N 99% of the POC was utilized. Alfalfa and corn leaf residues also showed sharp decreases in initial POC. Marked differences in C uptake were noted depending on the soil treatment and specific incubation period. An equation was developed which predicts C assimilation level and related soil biomass weights from decreases in POC.
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  • 99
    ISSN: 1573-5036
    Keywords: Calcium ; Magnesium ; Nitrogen ; Potassium ; Soil moisture ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of temperature and soil moisture levels on the chemical composition of wheat forage grown in growth chambers were studied. In addition to the environmental variables, K and N fertilization effects were studied. In all the studies, increasing levels of K fertilization depressed the Mg and Ca concentration of the shoots. Nitrogen fertilization increased the Mg concentration but had no effect on the Ca concentration of the plants. N fertilization depressed the K concentration in the soil moisture experiment, but had no effect on K concentration in the temperature experiment. Increasing the temperature from 10 to 20°C did not affect the Mg and Ca concentration of the shoots, but the K concentration declined due to dilution effects caused by the greater yield at the higher temperature. In the soil moisture level experiment the K, Mg and Ca concentration in wheat tended to decline with soil moisture level due to dilution effects. Calculations showed that uptake of K was regulated primarily by diffusion of K from the soil to the plant root and that the uptake of Mg was regulated by the uptake process of the plant root and not by the nutrient transport process through the soil.
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  • 100
    ISSN: 1573-5036
    Keywords: Eucalyptus marginata ; Lignotuber ; Nitrogen ; Phosphorus ; Seedlings ; Virgin soils X-ray probe microanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Jarrah seedlings were grown in six virgin Western Australian soils for up to 27 months. Lignotubers were produced in all soils and formed 10–16% of plant dry weight. The phosphorus concentration in the lignotuber (250–800 μg g−1) was nearly twice that in the stem and roots. The lignotuber contained 10–30% of total plant phosphorus and like the leaves was a sink for phosphorus. In one lateritic soil the phosphorus concentrations of lignotuber and stem barks were similar. However, in the same plants the concentration of phosphorus in the lignotuber wood was five times the phosphorus concentration in stem wood. Hence both lignotuber bark and sap wood in young jarrah seedlings are storage sites for phosphorus. X-ray probe analysis showed that wood phosphorus was associated with the ray parenchyma. Unlike phosphorus, nitrogen did not accumulate in the lignotuber and the concentrations of nitrogen were similar for roots, lignotubers and stems.
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