Models to predict nitrogen mineralization in soil

International audienc

C and N fluxes between pools of soil organic matter: Model calibration with long-term field experimental data

International audienceNCSOIL, an updated simulation model of C and N behaviour in soil, was calibrated with data from published field experiments in which various authors studied the decomposition of C- or N-labelled plant materials under a wide range of climatic and soil conditions. Four organic pools were included in the new version of NCSOIL viz. plant residues (decay rate constant = 0.3 d-1); microbial biomass with a labile (0.33 d-1) and a resistant (0.04 d-1) component; humads (0.006 d-1); and stable OM (5.5 10-5d-1). Experimental data were fitted with a reduction factor (REDI), which applied to all decomposition rates and for the whole of the simulated period. This parameter took into account the effect of climatic and soil conditions on microbial decomposition rates. Optimization of this reduction factor gave values which ranged from 0.06 to 1.0 and which were related well to the climatic and edaphic conditions given by the authors. Optimization of the size of the humads pool showed that the active soil organic fraction represented 13-35% of the total soil organic matter

Simulation Model of Nitrogen Tillage Residue Management System 3

38 pages

Models to predict nitrogen mineralization in soil

International audienc

C and N fluxes between pools of soil organic matter: Model calibration with long-term incubation data

International audienceAn updated version of the simulation model NCSOIL was calibrated with data from a long-term laboratory incubation (728 days at 28°C) of three cultivated soils amended with K 15NO3 and either [14C]glucose or [14C]cellulose. The kinetics of tracer and non-tracer C and N (CO2-C, inorganic-N and microbial biomass-C) were measured in the three soils on various sampling dates. The new NCSOIL version considers four organic pools: residues, microbial biomass (pool I) with two components (labile and resistant), humads (pool II) which correspond to the active fraction of soil organic matter (SOM), and pool III which is the highly resistant fraction of SOM.To fit the long-term incubation experimental data, it was necessary to reduce all decomposition rates by 60–70% after 35–85 days of incubation, depending on the soil and the treatment. The labile fraction of pool I in non-amended soils was also reduced to 0.20 from the previously-used value of 0.56; the later value, however, was adequate for the glucose and cellulose-enriched soils.Simulations agreed well with experimental data and gave values of pool II which represented about 30% of the SOM, and which had a C:N ratio of 12–13. Results suggested that >60% of the SOM was very resistant

Influence de la teneur en argile et du temps sur le taux de renouvellement et de stabilisation de la matière organique du sol

National audienc

Simulation by NCSOIL of net mineralization in soils from the deherain and 36 parcelles fields at Grignon

International audienc