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  • 1
    Electronic Resource
    Electronic Resource
    Modelling carbon and nitrogen dynamics in a bare soil with and without straw incorporation (2003)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 54 (2003), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Incorporating straw into the ploughed layer of soil affects the dynamics of carbon and nitrogen. A precise quantification of its short-term effect in agricultural fields is difficult because biological and physical processes interact and take place simultaneously. As an alternative to experimentation, investigations have turned to simulations using mechanistic models, and we have taken this approach. The goal of our study was to test a mechanistic and one-dimensional model of transport and biotransformation (PASTIS) against a data set obtained in a field experiment in northern France. We tested carbon and nitrogen dynamics by measuring C mineralization rates, the rates of gross immobilization and mineralization of N (using 15N tracing), and inorganic pools of N in the soil profile during 1 year in a bare soil with or without addition of wheat straw. Most of the model parameters were determined in independent experiments. We estimated the biological parameters from incubation experiments in the laboratory. The simulated results were in good agreement with experimental data, particularly for gross N rates. Hypotheses concerning the pathway of microbial assimilation and the dependence of decomposition on the size of the biomass were tested. The simulated net N immobilization due to addition of straw (8000 kg dry matter ha−1) reached a maximum of 64 kg N ha−1 after 2 months, whereas the observed value was 66 kg N ha−1. The model indicated that after 13 months the incorporation of straw had reduced the net amount of nitrogen mineralized by 13% and the amount of leached nitrate by 27%. The sensitivity analysis to the depth of straw incorporation indicated that the deeper was the incorporation the less was the leaching and the mineralization of nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2003.00499.x
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  • 2
    Electronic Resource
    Electronic Resource
    Redistribution of particulate organic matter during ultrasonic dispersion of highly weathered soils (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 56 (2005), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The use of ultrasonic energy for the dispersion of aggregates in studies of soil organic matter (SOM) fractionation entails a risk of redistribution of particulate organic matter (POM) to smaller particle-size fractions. As the mechanical strength of straw also decreases with increasing state of decomposition, it can be expected that not all POM will be redistributed to the same extent during such dispersion. Therefore, we studied the redistribution of POM during ultrasonic dispersion and fractionation as a function of (i) dispersion energy applied and (ii) its state of decomposition. Three soils were dispersed at different ultrasonic energies (750, 1500 and 2250 J g−1 soil) or with sodium carbonate and were fractionated by particle size. Fraction yields were compared with those obtained with a standard particle-size analysis. Undecomposed or incubated (for 2, 4 or 6 months) 13C-enriched wheat straw was added to the POM fraction (0.25–2 mm) of one of the soils before dispersion and fractionation. Dispersion with sodium carbonate resulted in the weakest dispersion and affected the chemical properties of the fractions obtained through its high pH and the introduction of carbonate. The mildest ultrasonic dispersion treatment (750 J g−1) did not result in adequate soil dispersion as too much clay was still recovered in the larger fractions. Ultrasonic dispersion at 1500 J g−1 soil obtained a nearly complete dispersion down to the clay level (0.002 mm), and it did not have a significant effect on the total amount of carbon and nitrogen in the POM fractions. The 2250 J g−1 treatment was too destructive for the POM fractions since it redistributed up to 31 and 37%, respectively, of the total amount of carbon and nitrogen in these POM fractions to smaller particle-size fractions. The amount of 13C-enriched wheat straw that was redistributed to smaller particle-size fractions during ultrasonic dispersion at 1500 J g−1 increased with increasing incubation time of this straw. Straw particles incubated for 6 months were completely transferred to smaller particle-size fractions. Therefore, ultrasonic dispersion resulted in fractionation of POM, leaving only the less decomposed particles in this fraction. The amounts of carbon and nitrogen transferred to the silt and clay fractions were, however, negligible compared with the total amounts of carbon and nitrogen in these fractions. It is concluded that ultrasonic dispersion seriously affects the amount and properties of POM fractions. However, it is still considered as an acceptable and appropriate method for the isolation and study of SOM associated with silt and clay fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1351-0754.2004.00654.x
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  • 3
    Electronic Resource
    Electronic Resource
    Carbon, nitrogen and microbial gradients induced by plant residues decomposing in soil (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 50 (1999), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Understanding the role of the soil matrix in the decomposition of soil organic matter requires an assessment of how the soil matrix controls the availability of substrate to microorganisms. We aimed to identify the sites of microbial assimilation of a decomposing substrate the initial location of which in the soil matrix was known. We incubated wheat straw doubly labelled with 13C and 15N as a single layer in the middle of a core of soil and we separated, after different times of incubation, soil layers situated at different distances from the straw. We analysed them for their 13C and 15N contents and dehydrogenase activity. The presence of the straw induced steep gradients of dehydrogenase activity in the core; the activity increased at the contact with the straw and decreased to reach the reference value between 3 and 4 mm from the straw. This stimulated microbial activity was linked with an incorporation of 13C derived from the straw in the core to approximately 4 mm from it. Nearly half of this 13C was present in the microbial biomass. Low temperature scanning electron microscopy showed that the microbial biomass was largest near the straw. The straw induced strong spatial heterogeneity of microbial activity at the millimetric scale, presumably because of diffusion of soluble compounds from the straw. This heterogeneity allowed us to identify the sites of microbial assimilation as being the soil nearest to the straw.〈section xml:id="abs1-2"〉〈title type="main"〉Gradients de carbone, d’azote et gradients microbiens induits par la décomposition de résidus végétaux dans le sol〈section xml:id="abs1-3"〉〈title type="main"〉RésuméPour comprendre le rôle de la matrice solide du sol sur la biodégradation des matières organiques il apparaît nécessaire d’étudier comment cette matrice contrôle l’accessibilité des substrats aux microorganismes. L’objectif de ce travail était de localiser les sites d’assimilation microbienne d’un substrat de localisation initiale connue. Pour cela, nous avons incubé de la paille de blé marquée 13C et 15N en couche médiane dans une éprouvette de sol, puis séparé, après différentes durées d’incubation, des tranches de sols situées à des distances croissantes du substrat, et nous avons mesuré leur teneur en 13C, 15N et leur activité déshydrogénase. La présence de paille a induit de forts gradients d’activité déshydrogénase, maximale au contact de la paille et décroissant ensuite pour atteindre la valeur de référence entre 3 et 4 mm du lit de paille. Cette stimulation de l’activité microbienne a été expliquée par l’incorporation dans l’éprouvette de sol, de 13C provenant de la paille, dont la moitié environ était présent dans la biomasse microbienne. Des observations en microscopie électronique à balayage à basse température ont montré de très forts développements microbiens au contact de la paille. La présence localisée d’un substrat organique de type paille a donc induit une forte hétérogénéité spatiale de l’activité microbienne, à des échelles millimétriques, vraissemblablement due à la diffusion de composés organiques solubles de la paille, dans le sol. On localise ainsi les sites d’assimilation microbienne du substrat dans le sol situéà une distance de moins de 4 mm de la paille.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.1999.00266.x
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  • 4
    Electronic Resource
    Electronic Resource
    Short-term kinetics of residual wheat straw C and N under field conditions: characterization by 13C15N tracing and soil particle size fractionation (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 48 (1997), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A clear understanding of the short-term decomposition and fate of crop residues is necessary to predict the availability of mineral N in soil. The fate of 13 C15N-labelled wheat straw in a silty soil (Typic Hapludalf) was studied using particle size fractionation and in situ incubation in which the equivalent of 8 t dry matter per ha of straw was incorporated into the soil over 574 days. Soil samples were separated into five particle-size fractions by wet sieving after disruption of aggregates. The weight, C and N contents, and 13C and 15N atom excess of each fraction were determined. Straw-derived C disappeared rapidly from the 〉 2000-μm fraction with an estimated half-life of 53 ‘normalized’ days (equivalent of 10°C and −0−01 MPA water potential). Straw-derived C appeared to be only temporarily stored in the intermediate fractions (1000–2000 and 200–1000 pm). The maximum net 13C accumulation in the 50–200-μm fraction was 4·4% of added 13C. Straw-derived C accumulated most rapidly and preferentially in the 50-μm fraction, which stabilized after 265 days and accounted for 70% of the residual 13C on day 574. Although there was more residual 15N than 13C, the distributions and kinetics of the two isotopes in the fractions were similar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1997.tb00548.x
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  • 5
    Electronic Resource
    Electronic Resource
    Fate of carbon and nitrogen in water-stable aggregates during decomposition of 13C15N-labelled wheat straw in situ (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 48 (1997), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: When incorporated in soil, plant residues and their decomposition products are in close contact with mineral particles with which they can be bound to form aggregates. We measured the incorporation of carbon (C) and nitrogen (N) derived from crop residues in water-stable aggregate fractions of a silty soil in a field experiment in Northern France using 13C15N-labelled wheat straw (Triticum aestivum L.). Soil samples were taken seven times for 18 months and separated into slaking-resistant aggregate size fractions which were analysed for total C and N contents, and 13C and 15N enrichments. During the early stages of decomposition (approximately 200 days), the enrichment of 13C increased rapidly in the macro aggregates (〉 250 pm) but decreased thereafter. The macro aggregates represented only 〈 20% of the soil mass and at any one time, they accounted for 〈25% of the residual 13C in the soil. The proportion of 13C recovered in the 〈50-μm and 50–250-μm fractions increased during decomposition of the residues; at day 574, the 50–250-μm fraction accounted for close to 50% of the residual 13C. A greater proportion of 15N than 13C was recovered in the 〈50-μm fraction. The results indicate that during decomposition in soil, C and N from crop residues become rapidly associated with stable aggregates. In this silty soil the 50–250-μm stable aggregates appear to be involved in the storage and stabilization of C from residues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1997.tb00549.x
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  • 6
    Electronic Resource
    Electronic Resource
    Spatial location of carbon decomposition in the soil pore system (2004)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    European journal of soil science 55 (2004), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We sought to examine the distribution of carbon (C) decomposition within the framework of the soil pore system. Soils were sampled from a transect having a natural gradient in pore-size distribution. After the addition of labelled wheat straw (13C) the repacked soil columns were incubated (25°C) at soil water matric potentials of either −75 kPa or −5 kPa and for either 4 or 90 days. Pore-size distribution was determined for each soil column after incubation and soils were then analysed for soluble C, label-derived residual C, label-derived and native biomass C, nematode abundance, and ergosterol concentration as an indicator of fungal biomass. Overall, the data suggested that pore-size distribution and its interaction with soil water give rise to a highly stratified biogeography of organisms through the pore system. This results in different rates of decomposition in pores of different size. Added plant material seemed to decompose most rapidly in soils with a relatively large volume of pores with neck diameters c. 15–60 µm and most slowly in soils with large volumes of pores with neck diameters 〈 4 µm. Regression analysis suggested that at matric potentials of both −75 kPa and −5 kPa the fastest decomposition of organic substrate occurred close to the gas–water interface. This analysis also implied that slower rates of decomposition occur in the pore class 60–300 µm. Correlations between the mass of soil biota and the pore volume of each pore class point to the importance of fungi and possibly nematodes in the rapid decomposition of C in the pores c. 15–60 µm during the early stages of decomposition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.2004.00639.x
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  • 7
    Electronic Resource
    Electronic Resource
    Biochemical Quality of Crop Residues and Carbon and Nitrogen Mineralization Kinetics under Nonlimiting Nitrogen Conditions (2000)
    Springer
    Soil Science Society of America journal 64 (2000), S. 918-926 
    Details
    ISSN: 1435-0661
    Keywords: CEL, cellulose fraction d.m., dry matter HEM, hemicellulose fraction LIG, lignin fraction POL, soluble polyphenols S20, soluble C fraction SOL, soluble fraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: −1 of added C. Mineralization kinetics were described using a two-compartment decomposition model that decomposes according to first-order kinetics. Amounts of C mineralized after 7 d and the decomposition rate coefficient of the labile fraction were related mainly to the soluble C forms of the residue. No statistical relationship was established between the N concentration of residues and their decomposition in the soil. The incorporation of crop residues into soil led to various soil mineral N dynamics. Two residues caused net N mineralization from the time of their incorporation, whereas all the others induced net N immobilization (1–33 g N kg−1 of added C). After 168 d, only residues with a C/N ratio 〈24 induced a surplus of mineral N compared with the control soil. The mineral N dynamics were related mainly to the organic N concentration of the residues and to their C/N ratio. At the start of incubation, these dynamics were also influenced by the presence of polyphenols in the plant tissues. Finally, this study showed the need to include the biochemical quality of crop residues in any C and N transformation models that describe decomposition. In contrast, the N concentration or C/N ratio of the residues are sufficient to predict the net effects of crop residues on soil mineral N dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 8
    Electronic Resource
    Electronic Resource
    Decomposition in the field of residues of oilseed rape grown at two levels of nitrogen fertilisation. Effects on the dynamics of soil mineral nitrogen between successive crops (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 125-137 
    Details
    ISSN: 1573-0867
    Keywords: Brassica napus L. ; plant residues ; decomposition ; N mineralisation ; N immobilisation ; modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The decomposition of oilseed rape residues of different quality and its effects on the mineral N dynamics of the soil in the period between crops were studied in situ. The residues studied were obtained by growing an oilseed rape crop at two levels of N fertilisation, 0 and 270 kg N ha-1. The study was carried out using two types of experiment: field plots and cylinders filled with disturbed soil and inserted into the soil. The decomposition of the residues was followed using an approach involving the dynamics of both carbon and nitrogen, the parameters measured being the CO2 emitted from the soil, the soil mineral N content, the C present in soluble form or in the form of microbial biomass, and the C and N present in the form of plant residues. The two residues studied, of similar biochemical composition, and differing only in their N content, were rapidly mineralised: approximately 50% of the carbon in the residues was decomposed during the first two months following incorporation into the soil. The carbon mineralised in the form of CO2 was largely related to the C present in the residues, no relationship having been found with the C present in soluble form or in the form of microbial biomass. Calculation of net N mineralisation from the residues using a model of mineralisation and leaching has provided evidence of an immobilisation phase for soil mineral N, during the first steps of residues decomposition. Labelling the high-N residues with 15N has moreover enabled us to demonstrate the low availability of the organic N from this residue, 20.8% of the organic N being mineralised in the course of 18 months of experimentation. Eventually, only the highest-N content residue resulted in a mineral N surplus in the soil, equivalent to 9 kg N ha-1, by comparison with the control soil. Finally, this study has provided good evidence of the complementarity between the two experimental methods. The cylinders of disturbed soil gave a precise measurement of the decomposition of the residues, especially by means of monitoring soil respiration. The field plots were used to monitor the dynamics of soil mineral N which were calculated with the aid of a mathematical model of mineralisation and leaching of nitrogen in the presence and absence of residues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009838618133
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  • 9
    Electronic Resource
    Electronic Resource
    The fate of labelled15N urea and ammonium nitrate applied to a winter wheat crop (1988)
    Springer
    Plant and soil 112 (1988), S. 205-214 
    Details
    ISSN: 1573-5036
    Keywords: ammonium nitrate ; inorganic nitrogen ; microbial immobilization ; N transformation ; 15N field experiment ; urea ; winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Labelled urea or ammonium nitrate was applied to winter wheat growing on a loamy soil in Northern France. Two applications of fertilizer were given: 50 kg N ha−1 at tillering (early March) and 110 kg N ha−1 at the beginning of stem elongation (mid-April). The kinetics of urea hydrolysis, nitrification of ammonium and the disappearance of inorganic nitrogen were followed at frequent intervals. Inorganic nitrogen soon disappeared, mainly immobilized by soil microflora and absorbed by the crop. Net immobilization of fertilizer N occured at a very similar rate for urea and ammonium nitrate. Maximum immobilization (16 kg N ha1) was found at harvest for the first dressing and at anthesis for the second dressing (23 kg N ha1). During the nitrification period, the labelled ammonium pool was immobilized two to three times faster than the labelled nitrate pool. No significant net15N remineralization was found during the growth cycle. The actual denitrification and volatilization losses were probably more important than indicated from calculations made by extrapolation of fluxes measured over short intervals. However microbial immobilization was the most important of the processes which compete with plant uptake for nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02139997
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  • 10
    Electronic Resource
    Electronic Resource
    The fate of labelled15N urea and ammonium nitrate applied to a winter wheat crop (1988)
    Springer
    Plant and soil 112 (1988), S. 215-224 
    Details
    ISSN: 1573-5036
    Keywords: ammonium nitrate ; fertilizer efficiency ; N dynamics ; N recovery ; 15N field experiment ; urea ; winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment was conducted on a winter wheat crop in Northern France with either15N-urea or ammonium nitrate, labelled either on NH4 or on NO3. The fertilizer was split between two dressings, one applied in early March and the second in mid-April, labelled separately. N uptake by the crop was measured at 8 successive times after each dressing. The N uptake efficiency of nitrate was higher than that of ammonium or urea over the whole growth cycle for both dressings. The RUC (Real Utilization Coefficient) reached a maximum at anthesis or even before anthesis, and decreased during the grain-filling period, indicative of N turnover in shoots. Thus the annual N use efficiency appeared highly dependent upon the date of measurement. At harvest, the contribution of soil N (residual N+mineralized N) to the crop was comparable to that from fertilizer, but the two pools were utilized at different periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02139998
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