Search

Crop residues are important inputs of carbon (C) and nitrogen (N) to soils and thus directly and indirectly affect nitrous oxide (N2O) emissions. As the current inventory methodology considers N inputs by crop residues as the sole determining factor for N2O emissions, it fails to consider other underlying factors and processes. There is compelling evidence that emissions vary greatly between residues with different biochemical and physical characteristics, with the concentrations of mineralizable N and decomposable C in the residue biomass both enhancing the soil N2O production potential. High concentrations of these components are associated with immature residues (e.g., cover crops, grass, legumes, and vegetables) as opposed to mature residues (e.g., straw). A more accurate estimation of the short‐term (months) effects of the crop residues on N2O could involve distinguishing mature and immature crop residues with distinctly different emission factors. The medium‐term (years) and long‐term (decades) effects relate to the effects of residue management on soil N fertility and soil physical and chemical properties, considering that these are affected by local climatic and soil conditions as well as land use and management. More targeted mitigation efforts for N2O emissions, after addition of crop residues to the soil, are urgently needed and require an improved methodology for emission accounting. This work needs to be underpinned by research to (1) develop and validate N2O emission factors for mature and immature crop residues, (2) assess emissions from belowground residues of terminated crops, (3) improve activity data on management of different residue types, in particular immature residues, and (4) evaluate long‐term effects of residue addition on N2O emissions. [ABSTRACT FROM AUTHOR]

Background and aims: Agroecology practices can induce profound positive changes in soil physical and chemical properties, and inevitably influence soil biological properties and soil functioning. However, we still lack understanding of how soil biodiversity responds to agroecology practices and to what extent such practices, alone or combined, can be beneficial for soil functioning and ecosystem services. Understanding soil biological activities under different agroecology practices is important for predicting carbon cycling in agroecosystems. Methods: By taking advantage of a long-term agricultural experimental research station in northern France, we monitored soil microbes, nematodes and soil respiration over three to five years in response to agroecology practices that varied in the rate of nitrogen (N) fertilization (low vs high), the tillage type (deep vs reduced), and the crop residue management (retain vs removal). Results: Shifting from conventional to agroecology practices had a strong effect on microbial biomass, nematode community and soil respiration. Specifically, reduced N and reduced tillage significantly increased microbial biomass carbon, bacterivore and fungivore density. Perennial biomass crop significantly decreased total nematode density and herbivore density, but increased microbial biomass carbon. Perennial biomass crop also significantly increased the structure and maturity index, but decreased the plant parasite index. Structural equation modelling showed that microbial biomass carbon had a positive correlation with soil respiration in reduced nitrogen, reduced tillage, and residue removal treatments. Bacterivores had a positive correlation with omnivores/predators and soil respiration, while herbivores had a negative correlation with soil respiration in all the treatments. Conclusions: The different agroecological practices tested in this 5-year trial revealed the resilience of nematode communities and associated functions like CO2 respiration according to practices. [ABSTRACT FROM AUTHOR]

The input of organic fertilizers into soils is an interesting option as a substitution for mineral fertilization, but how their interaction with crop residues affects the fate of added carbon (C) and nitrogen (N) in the soil is still poorly known. Therefore, we analysed the effect of adding together organic fertilizer and straw on subsequent C and N mineralization. We incubated sugarcane straw (S), pig slurry (PS) and solid sewage sludge (DS) separately and in mixtures (PS‐S and DS‐S) at 28°C during 182 days. To discuss interactions, we used a simple additivity model based on measurements and a mechanistic model for C and N transformations in soil (CANTIS). Both models overestimated the C mineralization and did not correctly predict N mineralization of the two mixtures. The differences between observed and expected values calculated with the models were negative for C mineralization, indicating an antagonistic interaction in mixtures. The limitations for C decomposition might be the result of many factors, such as negative priming effect or limitation in N accessibility, which are not considered by CANTIS. We assumed that the priming effect induced by the mineralization of a mixture was not significantly different from the priming effect induced by the mineralization of the organic matters incubated alone. The use of a contact factor in CANTIS allowed the predicted C and N kinetics for the mixtures to be correctly fitted to measured data. It reflects the effect of fine‐scale C and N distribution heterogeneities on the intensity of microbial decomposition. A better integration of the interactions between different N and C sources should be addressed to develop modelling as an accurate tool for agroecosystem management. Highlights: Experimental data and modelling allowed assessment of effects of mixtures on C and N mineralization.Mineralization of the organic material mixture was not the sum of the mineralization of each material.A contact factor reflecting the N‐rich substrate accessibility was needed to predict C and N data.Pig slurry and sewage sludge mixed with straw showed antagonistic effects on mineralization. [ABSTRACT FROM AUTHOR]

• The vertical decomposition gradient was characterized in mulches of various thicknesses. • Top mulch layers decomposed similarly, regardless of the thickness of the underlying mulch. • Low mulch layers decomposed faster as the thickness of the overlying mulch increased. • The decomposition gradient within the mulch was closely correlated with the moisture gradient. Crop residues left on the soil surface as mulch influence many services provided in agrosystems, particularly soil protection, water dynamics and nutrient fluxes. For a given crop, the residue mass influences the mulch thickness, but the effect of thickness on decomposition is not well understood, and decomposition gradients within mulches in the field have not been described. This study aimed to quantify the decomposition of sugarcane straw mulches by varying their mass and thickness and determine the decomposition gradient within the mulches. The experiment was conducted on a first-ratoon sugarcane crop for one year, with 4, 8 and 12 Mg straw dry matter ha−1. Mulches were displayed in 0.16-m2 litter boxes and formed by straw layers of equivalent mass, i.e., 4 Mg ha-1, stacked either as a single layer (Low/Top layer), 2 layers (Low and Top layers) or 3 layers (Low, Middle and Top layers) to reconstitute the 3 mulch quantities. We quantified the carbon (C) and nitrogen (N) contents, the chemical composition and the water content of the remaining mulch particles in each layer 10 times within the 360 days. The mulch degradation rates were proportional to the initial amount of straw, the mulch losses representing 75% of its initial C and 46% of its initial N after one year, regardless of the initial mass. Fertilizer-N addition did not change the k decomposition rate, with k = 0.0044 d−1. However the decomposition rate differed according to the layer position in the mulch, e.g., in the 12 Mg ha−1 treatment k = 0.0064 d−1, 0.0046 d−1 and 0.0033 d−1 for the low, middle and top layers, respectively, indicating that the low layers in contact with the soil decomposed faster than the top layers in contact with the atmosphere, while the medium layers demonstrated intermediate behaviour. The top layers evolved similarly, regardless of mulch thickness, while the lower layers in contact with the soil decomposed more quickly as the overlying straw thickness increased. Regardless of the thickness and position of a given layer within mulch, the one-year layer C loss was linearly correlated with the average water content of that layer over the year (y = 52.79 - 0694x, R2 = 0.991, P < 0.05). Here, we demonstrate that the dynamics of mulch decomposition is primarily driven by the dynamics of water, which is itself driven by mulch characteristics, rain regime and evaporation. [ABSTRACT FROM AUTHOR]

Background and aims: The use of summer cover crops (SCCs) as residue inputs in agricultural systems can lead to a potential environmental trade-off between the amount C and N retained and the emission of N as the potent greenhouse gas, nitrous oxide (N2O). Our objectives were to relate N2O fluxes to the quality of SCCs residues and to select SCCs species with high C and N addition and low N2O emissions.Methods: We measured SCC biomass production and N2O fluxes after SCCs termination - velvet bean, pearl millet, dwarf pigeonpea, sunn hemp, showy rattlebox and jack bean - under subtropical no-till conditions.Results: The N2O fluxes in the first 30 days after SCCs termination corresponded to 65% of cumulative N2O emissions measured during 165 days in 2010 and 150 days in 2011. The cumulative N2O emissions varied from 0.46 to 1.38 kg N ha-1 and were not proportional to aboveground biomass N addition. Cumulative N2O emissions were positively correlated to water-soluble C and N and the N content of crop residues and negatively correlated to cellulose and hemicellulose content. The N2O emission factor values varied from 0.24 to 0.64% and did not differ among SCCs.Conclusions: Sunn hemp and dwarf pigeonpea are the most suitable species for inclusion in crop systems because they combined high C and N input and low N2O emissions. [ABSTRACT FROM AUTHOR]

Background and aims: Crop residues and soil types play an important role in soil C and N storage. The objectives of this study were to quantify the effects of crop residue quality and interactions with soil type on soil C and N, in the short- and medium-term, and to determine the responses related to the priming effect (PE). Methods: Residues of vetch ( Vicia sativa L.), pea ( Pisum sativum L.) and wheat ( Triticum aestivum L.) crops with different chemical compositions and labelled with C and N were left to decompose on the surface of either a sandy-loam soil or a clay soil incubated under laboratory conditions at 25 °C for 360 days. We measured the total CO-C and CO-C emitted during decomposition, the soil mineral N content and the amounts of C and N remaining in both the surface residue particles and the bulk soil. Results: Over the short-term, the vetch residues decomposed faster than those of wheat and pea on the soil surface due to their more favourable chemical composition for biodegradation; after one year, however, this difference disappeared. We observed extra soil C mineralization in all cases, i.e., the PE was positive for all treatments and was directly related to the water-soluble (vetch > pea > wheat) and soil C contents (clay soil > sandy-loam soil). Conversely, the fate of the added N and net N mineralization differed considerably between the three residues and was strongly related to the initial N content of the residue. Conclusions: Crop residue quality and soil type affected the soil PE and soil C balance but not the fate of crop residue-C after one year. Net soil N mineralization was observed in all crop residues, with large early differences (vetch > pea > wheat), which were maintained on a medium-term basis. Our results emphasize the need to jointly consider C and N dynamics as well as short- and medium-term effects to manage agricultural and environmental services provided by the recycling of crop residues to agricultural soils. [ABSTRACT FROM AUTHOR]

The accurate quantification of crop residue biomass left on the soil after harvesting is important, due to the agricultural and environmental issues associated with the management of soil organic matter in croplands. This quantification is difficult in farmers' fields due to a high variability of crop residue distribution on soil surface, because of harvesting operations. The objective of this study was to provide, for measuring crop residue biomass in the field, an accurate, robust and generic method for a large range of crops. This method relies on the use of sampling microplots (0.5 × 0.5 m), located along a transect and taking into account harvesting operations (harvesting direction and width) to capture this variability. This method was tested from 2009 to 2011, in farmers' plots after harvesting, on wheat, grain maize, spring barley, field pea, rapeseed, fababean and sunflower crops. The comparison of results obtained with one or two transects (one perpendicular and the other diagonally across harvesting direction) shows that the accuracy of the estimates is sufficient using a single transect, allowing for a reduction of the working time. The accuracy of this method of collection is not affected by soil management practices (shallow till versus no-till). [ABSTRACT FROM AUTHOR]

Aims: The role of precipitation on the decomposition of residue mulches is of primary importance for the adequate management of nutrients in no-tilled agrosystems. The objective of this work was to understand the interactions between water dynamics and crop residue quality and their effect on carbon (C) and nitrogen (N) mineralization. Methods: The decomposition of two residue mixtures (wheat + alfalfa and maize + lablab) left at the surface of repacked soil columns, was studied under controlled conditions, at 20 °C over 84 days. Simulated rain pulses were either light and frequent or heavy and infrequent. A loamy soil (Luvisol) and a sandy soil (Ferralsol) were used. Results: The maize/lablab mulch remained wetter between rain pulses which induced greater decomposition than the wheat/alfalfa mulch. Frequent/light rain pulses maintained the mulches wetter between pulses than infrequent/heavy rain pulses, and therefore these mulches decomposed faster. The loamy soil favored the moistening of the mulch layer in contact with the soil which enhanced its decomposition, compared to the sandy soil. Conclusions: The water dynamics (water content of the mulches and soil, evaporation, and drainage) was highly modified by residue quality, rain regime and soil type, which in turn significantly affected the mineralization of C and N. [ABSTRACT FROM AUTHOR]

The effects of plant litter characteristics on its decomposition in soil or at the soil surface is of primary importance for adequate management of nutrients and carbon (C) in agro-ecosystems. However, understanding the influence of mixtures of residues, which is actually the most common situation encountered in agriculture, is still poorly known in cultivated soils. Therefore we analyzed the effect of mixing leaf and stem litters from 25 species of plants (main crops and cover crops), representative of agricultural systems in subtropical conditions, on subsequent C and nitrogen (N) mineralization. We characterized the chemistry of leaves, stems and mixtures and determined the heterogeneity of the mixtures using Gower's similarity coefficient. We incubated crop residues at the surface of a sandy loam soil at 25 °C over 120 days and continuously measured the mineralization of C and N. The 25 mixtures represented a wide range of chemical qualities and heterogeneity. Significant differences in C mineralization and soil N accumulation clearly differentiated crop families (notably Poaceae species vs. Fabaceae species), and plant parts (stems vs. leaves). The differences between observed and expected values for C mineralization were low or nil, indicating mostly an additive effect of mixing. Significant synergetic effects existed for only 7 species and resulted in an average additional 9% C mineralized. For N, an antagonistic effect was observed only with Fabaceae mixtures having high average N content and high chemical heterogeneity. We concluded that the decomposition of mixtures appeared mainly controlled by their average chemical composition and to a less degree by their chemical heterogeneity. In these cases, the availability of N in the mixtures appeared to increase the microbial N immobilization, reducing the net accumulation of mineral N in the soil. [ABSTRACT FROM AUTHOR]

The availability of soil nutrients, which are recycled through the decomposition of crop residues, is important for the management of cropped soils. However, knowledge regarding the influence of contact between crop residues and soil on the dynamics of carbon (C) and nitrogen (N) in soil is limited. In particular, the effect of particle size on decomposition is not well-known, and conceptual approaches for modelling the soil-residue contact in a decomposition model remain scarce. Therefore, we analysed and modelled the effect of maize stem particle length on decomposition. We incubated maize stem residues with particle sizes of 0.02, 0.5, 2 and 5 cm in length in a loamy soil at 25 °C over 301 days. We continuously measured the mineralisation of C and N and determined the chemical evolution of the remaining particles. We used the decomposition model CANTIS which takes into account the soil-residue contact, using a contact factor, K. The decomposition rates of smaller maize particles were higher than those of larger particles during the early phases of decomposition. However, these differences were not maintained after 301 days. These results suggest that a larger size of the maize particles only slowed the rate of mineralisation in the short term but did not modify decomposition in the medium term. We proposed a new formalism for expressing the changes in soil-residue contact with different particle sizes. The contact factor K was calculated using the standardised specific surface area and can be applied more widely to residues that differ in morphology and density. [ABSTRACT FROM AUTHOR]

The joint management of animal manures and plant biomass as straw on agricultural soils may be a viable option for reducing the environmental impacts associated with livestock production and recycling nutrients efficiently. To investigate this option, an incubation in controlled conditions examined how the simultaneous addition of N-labeled pig slurry and C-labeled wheat straw, either on the soil surface or incorporated into the soil, affected the mineralization of C from the organic materials and the soil N dynamics. Samples from a typic hapludalf were incubated for 95 days at 25°C with eight treatments: unamended soil (S), wheat straw left on the soil surface (Ws), wheat straw incorporated in the soil (Wi), pig slurry on the soil surface (Ps), pig slurry incorporated in the soil (Pi) and three combinations of the two amendments: Pi + Ws, Pi + Wi, and Ws + Ps. Carbon dioxide and CO emissions and soil N content were measured throughout the incubation. Pig slurry stimulated the decomposition of straw C only when wheat straw and pig slurry were left together on the soil surface. Incorporation of both wheat straw and pig slurry did not modify straw C mineralization when compared to straw incorporation alone but this promoted a higher rate of N immobilization. The results suggest that when pig slurry is used in field under no-till conditions, the best strategy to preserve environmental quality with regard to CO emissions would be to apply pig slurry underneath the crop residues. [ABSTRACT FROM AUTHOR]

• Management of crop residues influences residue-derived N 2 O emissions. • Major environmental drivers of N 2 O emissions are affected by mulch mass and quality. • Vetch mulch increased soil available C and N and N 2 O emitted compare to wheat mulch. • Crop residue emission factors should consider the effects of mulch on soil functions. Crop residue affects nitrous oxide (N 2 O) emissions in no-tillage systems, but the magnitude of the emissions depends on soil drivers that are directly influenced by crop residue quality and quantity. We conducted a one-year study to investigate how mulch chemical characteristics and mass affect N 2 O emissions during their decomposition in the field under subtropical conditions. The mulch treatments consisted of vetch and wheat crop residues applied to the soil at quantities of 0, 3, 6 and 9 Mg ha−1 dry matter. We followed the kinetics of mulch carbon (C) and nitrogen (N), soil temperature, moisture and inorganic N, the denitrification end-product ratio [N 2 O/(N 2 O + N 2)] at days 15 and 30, and N 2 O and carbon dioxide (CO 2) emissions with a static chamber method. Mulch decomposition and C and N dynamics were very rapid for vetch and much more gradual for wheat, reflecting the differences in their initial chemical compositions, but for both residues, the initial mulch mass had no effect on the decomposition rate. The presence of mulches increased soil moisture in the 0–10 cm soil layer, with the results for water-filled pore space by treatment as 0 = 3 < 6 = 9 Mg ha−1. Vetch also significantly increased the inorganic N content in the soil, unlike wheat, which caused net N immobilization. The daily N 2 O fluxes were strongly and positively correlated with CO 2 fluxes (r = 0.83). The highest N 2 O fluxes were observed in the first 60 days with the vetch residues, and the results increased by treatment as 0 < 3 < 6 = 9 Mg ha−1; for wheat, the mean N 2 O emitted was 50% lower than that for vetch and was not affected by mulch mass. Although the cumulative N 2 O emitted was higher in vetch than in wheat, the N 2 O emission factor was higher for the wheat than for the vetch residues (EF = 4.64% vs 1.75% of N applied). We conclude that while mulch mass and quality strongly influenced soil drivers of N 2 O emissions, not only the N input but also the nature of residue C and the residue location must be taken into account to understand and predict N 2 O emissions associated to crop residue management. [ABSTRACT FROM AUTHOR]

Banana crops in the Caribbean are characterized by the use of high rates of nitrogen (N) fertilization which causes severe environmental damages. The aim of this study was to assess the fertilizer N use efficiency (NUE) of banana crops in the field. To do so, a field trial was carried out during the first (GS1) and the fourth (GS4) growing seasons of banana crops, and the fate of a 15N-labeled pulse applied late in the growing season (flowering stage) was determined. At harvest, NUE (average 24% 15N applied) and the total recovery of fertilizer 15N in the soil–plant system (i.e., 40% in GS1 and 62% in GS4) were low. Low NUE resulted mainly from the dilution in a large soil mineral N pool derived from earlier applications of the labeled-N fertilizer applied at flowering, combined with leaching caused by numerous high-intensity rainfall events (>20 mm d−1). Crop residues from previous cycles present at time of fertilizer application in the fourth growing season, promoted fertilizer N immobilization, which in turn favored fertilizer N recovery by decreasing N leaching. The results suggest that N fertilization after the first season could be reduced by 30% (i.e., −90 kg N ha−1) corresponding to the suppression of two applications from flowering to harvest with the current fertilizer management, as available N derived from earlier applications is sufficient to meet plant requirements. [ABSTRACT FROM AUTHOR]

In no-tillage systems, crop residues are left on the soil surface and form a mulch, which can result in the stimulation of N 2 O emissions through various processes. As a consequence, the accurate description of mulch decomposition and the associated N 2 O emissions by soil-crop models is essential to help manage the potential impacts of mulches on the environmental performances of these agroecosystems. Here, we combined the use of a soil-crop model (STICS) and published experimental data to develop a new model representation of mulches (with various masses and qualities) and their decomposition, the carbon (C) and nitrogen (N) dynamics, and effects on N 2 O emissions. We used a published dataset from southern Brazil combining two residues with distinct chemical characteristics (vetch, Vicia sativa L., and wheat Triticum aestivum L.) and four rates of mulch addition (0, 3, 6 and 9 Mg dry matter (DM) ha−1) decomposing over one year. The STICS model with its default parameterization overestimated the remaining mulch masses, particularly at high DM inputs, and underestimated the N 2 O emissions. The evolution of the STICS soil and decomposition modules led to two major results: i) we modified the mulch module parameterization, by representing that the whole mulch is accessible to decomposers, whatever its initial mass and thickness; ii) a new potential denitrification function was proposed, which uses simulated CO 2 fluxes associated from both soil humus and residue decomposition as proxy for C readily available to denitrifiers. With these new representation and parameterization, the model then accurately reproduced the very large range of magnitudes and the temporal variability of C and N fluxes observed for the two residues and the four mulch masses. These results are promising and the conceptual formalisms generic enough to be potentially developed in other soil-crop models. The next step is now to extend and generalize them to other conditions. [Display omitted] • Mulches of four masses resulted in similar carbon dynamics and wide N 2 O emissions. • The STICS model needs improvements in mulch decomposition and the induced stimulation of N 2 O emissions. • The entire mulch was considered accessible to decomposers regardless of its initial mass and thickness. • The CO 2 emitted, considered a proxy of C availability, was used to define the denitrification potential. [ABSTRACT FROM AUTHOR]

• Soluble C leaching from mulches by rain is an important pathway for soil C cycling. • Interception of water by mulches depends on the residue type and amount of rain applied. • Rain leached a large proportion of the initial residue water-soluble C. • High rainfall intensity was less effective than low intensity at displacing soluble C. The presence of crop residues on the soil surface of no-till cropping systems has important consequences on water flows between the atmosphere, litter layer (mulch) and soil. The consequences of rainfall on the transport of soluble C from litter layers are poorly known, despite their importance for soil carbon (C) and nutrient cycling. We quantified relationships among the rain amount and intensity, the water retention by mulches and the soluble C loss from mulches under rainfall. Mulches of residues from mature crops (maize, soybean and rice) and a cover crop (pea) were placed under continuous simulated rains with intensities of 4, 11 and 24 mm h−1 for 23 h, and we measured the water interception dynamics of the mulches and the water and soluble C flows under the mulches. The maximal water contents of the pea, maize and rice mulches did not differ significantly from each other (5.9–6.6 g H 2 O g−1 dry matter), while the soybean mulch retained much less water than the other mulches at 3.5 g H 2 O g−1 dry matter (DM). The soluble C loss was 9.2–23.7 % (4 mm h−1) and 19.3–55.2 % (24 mm h−1) depending on the residue type after 7 h of rain. With similar amounts of received rain (500 mL), the soluble C loss was identical for intensities at 4 and 11 mm h−1, and significantly lower at 24 mm h−1, suggesting inefficient rain transport at the high rain intensity. Finally, this study highlights the importance of better characterizing the physical and water properties of mulches and residue particles because of their significant effects on water and soluble C transport. [ABSTRACT FROM AUTHOR]

Crop residues are the main source of carbon (C) inputs to soils in cropping systems, and their subsequent decomposition is crucial for nutrient recycling. The interactive effects of residue chemical quality, residue placement and soil mineral nitrogen (N) availability on carbon and N mineralization dynamics were experimentally examined and interpreted using a modelling approach with the deterministic-functional, dynamic decomposition module of the Simulateur mulTIdisciplinaire pour les Cultures Standard (STICS) model. We performed a 120-day incubation at 25 °C to evaluate how the mineralization of C and N from residues would respond to residue type (residues of 10 crop species with C:N ratios varying from 13 to 105), placement (surface or incorporated) and initial soil mineral N content (9 or 77 mg N kg−1 dry soil). A reduced C mineralization rate was associated with N limitation, as observed for high-C:N ratio residues, and shaped by residue placement and initial soil mineral N content. This was not observed for low-C:N ratio residues. Overall, increased net N mineralization corresponded with reduced N availability. Using the optimization procedure in the STICS decomposition module to explain the C and N dynamics of surface-decomposing residues, we estimated that 24% of the total soil mineral N would be accessible to decomposers. The STICS decomposition module reproduced the C and N dynamics for each treatment well after five parameters were optimized. The optimized values of the biomass C:N (CNbio) , residue decomposition rate (k), humification coefficient of microbial C (h), and microbial decomposition rate (λ) were significantly correlated with total N availability across all 40 treatments. Under low total N availability, CNbio increased, while k , h and λ decreased compared to their values under high N availability, suggesting functional changes in the microbial community of decomposers. Our results show that an N availability approach could be used to estimate residue C dynamics and net N mineralization in the field in response to crop residue quality and placement and demonstrate the potential to improve decomposition models by considering the effects of N availability on C dynamics. • Crop residue quality and their placement in soil interact during decomposition. • Soil surface placement and high C:N ratios in residue reduce N availability to decomposers. • Low N availability decreases residue C mineralization and microbial N immobilization. • Residue degradation rate and biomass C:N ratio are controlled by the total N availability. • The N limitation concept should improve predictions of net N mineralization. [ABSTRACT FROM AUTHOR]

Abstract: Crop residue management has been shown to significantly affect the decomposition process of plant debris in soil. In previous studies examining this influence, the extrapolation of laboratory data of carbon and/or nitrogen mineralization to field conditions was often limited by a number of interactions that could not be taken into account by a mere experimental approach. Therefore, we demonstrated the interactive effect between crop residue location in soil (mulch vs. incorporation) and its biochemical and physical quality, in repacked soil columns under artificial rain. Decomposition of 13C and 15N labelled rape and rye residues, with associated C and N fluxes, was analysed using the mechanistic model PASTIS, which turned out to be necessary to understand the interacting factors on the C and N fluxes. The influence of soil and residue water content on decomposition and nitrification was evaluated by the moisture limitation factor of PASTIS. This factor strongly depended on residue location and to a smaller extent on physical residue properties, resulting in a lower decomposition rate of about 35% for surface placed compared to incorporated residues. Irrespective of its placement, the biochemical residue quality (e.g. N availability for decomposition, amount of soluble compounds and lignin) was responsible for a faster and more advanced decomposition of about 15% in favour of rye compared to rape, suggesting only a limited interaction between residue quality and its location. Net N mineralization after nine weeks was larger for rye than for rape, equivalent to 59 and 10kg NO3 −–Nha−1 with incorporation, and 71 and 34kg NO3 −–Nha−1 with mulch, respectively. This net N mineralization in soil resulted from the interaction between soil water content, depending on residue placement, and N availability, which was determined by the biochemical residue quality. Moisture limitation appeared more important than N limitation in the decomposition of mulched residues. Modelling of gross N mineralization and immobilization also revealed that leaving crop residues at the soil surface may increase the risk of nitrate leaching compared to residue incorporation, if (i) soil water content under mulch is larger than with residue incorporation (more gross N mineralization), and (ii) availability to the applied C-source is limited (less gross N immobilization). Scenario analyses with PASTIS confirmed the importance of moisture conditions on the decomposition of mulched residues and the small interaction between biochemical crop residue quality and its location in soil. [Copyright &y& Elsevier]