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  • 1
    ISSN: 1573-5036
    Keywords: ammonia volatilization ; anhydrous ammonia ; sandy loam ; soil water content ; wind tunnels
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Laboratory experiments have shown appreciable losses of ammonia after injection of anhydrous ammonia into dry and wet soils. In this study losses of ammonia injected into a moist (tension 10 kPa), dry (tension 160 kPa) and a wet (tension 1.6 kPa) sandy loam were measured under field conditions using wind tunnels. Losses were insignificant from a moist soil. However losses from a dry and a wet soil were 20% and 50% of injected ammonia, respectively. From the dry soil, losses of gaseous ammonia took place within the first hours after injection, which indicates a rapid transport through cracks and voids. From the wet soil, 20% of the injected ammonia was lost more gradually between 6 h and 6 d. This indicates that upward movement of water due to evaporation may be the cause of these ammonia losses which proceeded for longer periods.
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  • 2
    ISSN: 1432-0789
    Keywords: Key words European soils ; Moisture ; Nitrogen immobilization ; Temperature ; Wheat straw
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Wheat straw enclosed in mesh bags was buried for periods up to 1 year over two seasons in Scottish, Danish and Portuguese soils treated with 15NH4NO3 or NH4 15NO3. Scottish soils were: Terryvale, a poorly drained sandy loam; and Tipperty, an imperfectly drained brown forest soil with a higher clay content. The Danish soil (Foulum) was a freely drained sandy loam and the Portuguese soils were a sandy soil (Evora) and a clay soil (Beja). During the first month, 15N was being incorporated into the straw in the Tipperty, Terryvale and Foulum soils simultaneously as the total N content was decreasing. Subsequently, the straws began to show net immobilization and the total N content of the original straw was exceeded in Tipperty and Foulum soils after 4 months and 8 months, respectively. Net immobilization in Terryvale was detected only in the second season and did not occur in the first because of high soil moisture content. The rates of 15N incorporation were similar in the two Portuguese soils, and a loss of N was only detected after 8 months. After 1 month, in the two clay soils, Beja and Tipperty, 15NO3 – was incorporated into straw to a greater extent than 15NH4 + and this was attributed to 15NH4 + fixation by clay minerals. In contrast, 15NH4 + was more efficiently incorporated than 15NO3 – under waterlogged conditions (Terryvale) and NO3 – loss could be attributed to denitrification. The proportion of added 15N in the straw residue after 1 month varied between 6% and 18% for 15NH4 + and 2% and 23% for 15NO3 – and immobilization of N in the longer term tended to be greater in soils from northern Europe than from Portugal.
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  • 3
    ISSN: 1432-0789
    Keywords: Mineral-fixed ammonium ; Non-exchangeable ammonium ; Soil particle-size fractions ; Soil texture ; 15N ; N turnover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Four soils with 6, 12, 23, and 47% of clay were incubated for 5 years with 15N-labeled (NH4 2SO4 and hemicellulose. The incubations took place at 20°C and 55% water-holding capacity. Samples of whole soils, and clay- (〈2 μm) and silt-(2–20 μm) size fractions (isolated by ultrasonic dispersion and gravity sedimentation) were analysed for labeled and native mineral-fixed ammonium. Mineral-fixed ammonium in non-incubated soil samples accounted for 3.4%–8.3% of the total N and showed a close positive correlation with the soil clay content (r 2 = 0.997). After 5 years of incubation, the content of mineral-fixed ammonium in the clay fraction was 255–430 μg N g−1, corresponding to 71%–82% of the mineral-fixed ammonium in whole soils. Values for silt were 72–166 μg N g−1 (14%–33% of whole soil content). In the soils with 6% and 12% clay, less than 1 % of the labeled clay N was present as mineral-fixed ammonium. In the soil with 23% clay, 3% of the labeled N in the clay was mineral-fixed ammonium. Labeled mineral-fixed ammonium was not detected in the silt fractions. For whole soils, and clay and silt fractions, the proportion of native N present as mineral-fixed ammonium varied between 3% and 6%. In contrast, the proportion of labeled N found as mineral-fixed ammonium in the soil with 4701o clay was 23%, 38% and 31% for clay, silt, and whole-soil samples, respectively. Corresponding values for native mineral-fixed ammonium were 12%, 16%, and 10%. Consequently, studies based on soil particle-size fractions and addressing the N turnover in clay-rich soils should consider the pool of mineral-fixed ammonium, especially when comparing results from different size fractions with those from fractions isolated from soils of a widely different textural composition.
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  • 4
    ISSN: 1435-0661
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 15 N-labeled urine, feces, or straw, or unlabeled components only. The urine and feces were from a sheep first fed unlabeled hay and then 15N-labeled hay. Manures (≈ 19 g total N m-2) were incorporated into two coarse-textured soils before planting to spring barley (Hordeum vulgare L.) undersown with perennial ryegrass (Lolium perenne L.). Manures with one 15N-labeled component were supplemented with unlabeled NH4 15NO3 (7.3 g N m-2), while unlabeled manure was given 15NH4 15NO3. Labeled and unlabeled N were determined in the spring barley at maturity and in six cuts of ryegrass taken during the succeeding 2.5 yr. The homogeneity of feces and urine 15N-labeled was high. Dry matter yields and crop N offtakes were similar in all treatments. Barley (grain and straw) recovered 40, 26, 10 and 6% , respectively of 15N added with mineral fertilizer, urine, straw, and feces. Weighted mean recovery of the combined manure and fertilizer dressing was 22% of the added 15N higher than reported in previous studies on individual components, indicating that the N mineralization-immobilization turnover (MIT) of the manure components interacted. In the second and third growth seasons, 2.7 to 4.4% and 1.1 to 2.0% of the 15N was recovered in grass cuts, respectively. Total recovery ranged from 84 to 95% of the added 15N, suggesting small N losses from this cropping system.
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  • 5
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: With annual incorporation of straw, soil N mineralization is expected to increase whereby requirements for fertilizer N inputs may be reduced. Samples of whole soil, clay (〈 2 μm), silt (2–20 μm) and sand (20–2000 μm) sized organomineral separates from three soils with annual additions of straw ranging from 0 to 12 t ha–1 were leached after 0, 1, 2, 4, 8, 12 and 16 weeks of incubation at 20°C, to determine the content of NH4 + NO3. A three-pool model using first order kinetics and fixed rate constants (N1, k1 = 0.231 day–1; N2, k2 = 0.00693 day–1; N3, k3 = 0) was fitted to the mineralization data.The mineralizability of whole soil N (mg N g–1 N) differed among soil types. Straw generally increased the fast N1 and the passive N3 pool while the medium-term N2 pool was reduced in size. The N1, N2 and N3 averaged 0.8, 2.6 and 96.6% of the whole soil N, respectively.The N mineralizability increased in the order: sand 〈 silt 〈 clay. The lability of N in a given size separate was almost similar across soil types and straw managements. The active N pools (N1 + N2) averaged 7.1% of the clay N and 2.2% of the silt N. The main difference was related to the N2 pool, which accounted for 5.5% in clay and 1.2% in silt.Mineral N produced during incubation ranged from 63 to 105 kg N ha–1. Effects of straw disposal were small (〈 11 kg N ha–1). Maximum response was at 4 t straw ha–1; adding more straw diminished mineralization of N.Long-term annual incorporation of cereal straw contributes mainly soil N with a slow turnover.
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  • 6
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Physical fractionation is used increasingly to study the turnover of organic matter in soil. This essay links the methods of fractionation to concepts of turnover by defining levels of structural and functional complexity that refer to experimentally verifiable pools of organic matter in the soil.Physical fractionation according to size and density of soil particles emphasizes the importance of interactions between organic and inorganic soil components in the turnover of organic matter. It allows the separation of free and occluded uncomplexed organic matter and of primary and secondary organomineral complexes. This methodological approach recognizes that the overall regulation of decomposer activity is through the structure of soil, which determines gas exchange, the availability of substrates and water, and the transport of solutes.Results from physical fractionations suggest three levels of structural and functional complexity in the turnover of organic matter in soil. Primary organomineral complexes isolated from fully dispersed soil account for the primary level of complexity. The clay-, silt- and sand-sized complexes are seen as the basic units in soil, surface reactions between substrates, organisms and minerals being the main regulatory mechanisms. Secondary complexes reflect the degree of aggregation of primary organomineral complexes and refer to the second level of complexity. Physical protection of uncomplexed organic matter and soil organisms and the creation of gas and moisture gradients are emergent features regulating the turnover at this level of complexity. The structurally intact soil (the soil in situ) constitutes the third level of complexity. This integrates the effects of primary and secondary complexes. Emergent structural features associated with this level are resource islands, macropores, roots, mesofauna, tillage and soil compaction, the corresponding functional features being related to the transport and exchange of solutes and gases, and the spatial distribution and comminution of litter and uncomplexed organic matter. Thus, a thorough understanding of the turnover and storage of organic matter in soil can be acquired only by considering all levels of complexity in the decomposition subsystem.
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  • 7
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Leaching of nitrate from a sandy loam cropped with spring barley, winter wheat and grass was compared in a 4-year lysimeter study. Crops were grown continuously or in a sequence including sugarbeet. Lysimeters were unfertilized or supplied with equivalent amounts of inorganic nitrogen in calcium ammonium nitrate (CAN) or animal slurry according to recommended rates (1N) or 50% above recommended rates (1.5N).Compared with unfertilized crops, leaching of nitrate increased only slightly when 1N (CAN) was added. Successive annual additions of 1.5N (CAN) or 1N and 1.5N (animal slurry) caused the cumulative loss of nitrate to increase significantly. More nitrate was leached after application of slurry because organic nitrogen in the slurry-was mineralized.With 1N (CAN) the leaching losses of nitrate were in the following order: continuous spring barley undersown with Italian ryegrass 〈 continuous ley of perennial ryegrass 〈 spring barley in rotation and undersown with grass 〈 perennial ryegrass grown in rotation = winter wheat grown in rotation 〈 sugarbeet in rotation 〈 continuous winter wheat 〈 continuous barley 〈 bare fallow.At recommended levels of CAN (1N), cumulative nitrate losses over the four years were similar for the crops when grown in rotation or continuously. When crops received 1.5N (CAN) or animal slurry, nitrate losses from the crops grown continuously exceeded those from crops in rotation. Including a catch crop in the continuous cropping system eliminated the differences in nitrate leaching between the two cropping systems.
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  • 8
    Publication Date: 2010-01-05
    Print ISSN: 1726-4170
    Electronic ISSN: 1726-4189
    Topics: Biology , Geosciences
    Published by Copernicus on behalf of European Geosciences Union (EGU).
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  • 9
    Publication Date: 1985-06-01
    Print ISSN: 1351-0754
    Electronic ISSN: 1365-2389
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 10
    Publication Date: 1986-06-01
    Print ISSN: 1351-0754
    Electronic ISSN: 1365-2389
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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