Quantifying and modelling C and N mineralization kinetics of catch crop residues in soil: parameterization of the residue decomposition module of STICS model for mature and non mature residues

Abstract

C and N mineralization kinetics of 25 catch crop (CC) residues, whose organic C:N ratio varied from 9.5 to 34.0, were studied during soil incubations under controlled conditions. Decomposition rates were rather similar for the different CC residues, 59% to 68% residue-C being mineralized after 168 days incubation. C mineralized during the first weeks was mainly correlated to the soluble C content of the residue. N mineralized from CC residues was much more variable (−4.9 to +38.0 mg N g −1 added C at day 168), and was mainly related to the organic N content in residues. C and N mineralization kinetics were simulated with STICS residue decomposition model, using the previous parameterization mostly based on mature crop residues (Nicolardot et al. Plant Soil 228:83-103, 2001). A reasonable agreement was found between measured and simulated C kinetics but N mineralization was underestimated by the model. A new parameterization was carried out to improve N predictions. The fitting procedure was first applied independently to each CC residue in order to optimise the five parameters of the model. The relationships found between each optimised parameter and the C:N ratio of CC residues were similar to those obtained previously, indicating that the same model was applicable to all residues. The parameters of these relationships were fitted on a combined dataset including CC and mature residues. The new parameterisation lead to better simulations for CC residues, the errors of prediction (RMSE) for C and N mineralization being 32 and 1.8 mg g −1 added C, respectively. For the whole dataset (68 residues), the RMSE were 50 and 3.3 mg g −1 added C. The prediction quality is satisfactory with respect to the model simplicity and the single criterion of residue quality (C:N ratio).

Influence of root and leaf traits on the uptake of nutrients in cover crops

“…In contrast to mineral fertilizers, nutrients accumulated by cover crops are released progressively and cover crop mineralization can be coordinated with subsequent crop needs. For this purpose, C/N ratio can be used as an indicator of the dynamics and the rate of mineralization (Justes et al 2009). With C/N ratio values above 26, it has been shown that a net immobilization of N by soil microorganisms occurs within the first weeks (Justes et al 2009).…”

“…For this purpose, C/N ratio can be used as an indicator of the dynamics and the rate of mineralization (Justes et al 2009). With C/N ratio values above 26, it has been shown that a net immobilization of N by soil microorganisms occurs within the first weeks (Justes et al 2009). Mineralization rate is also reduced and strong pre-emptive competition can occur (Thorup-Kristensen and Dresbøll 2010).…”

“…Mineralization rate is highly dependent on residue quality, which evolves with time, and can be appraised through the C/N ratio. Justes et al (2009) observed that a C/N ratio below 26 should be favorable for mineralization. Above this threshold, immobilization of the nutrients occurs.…”

Soil mineral nitrogen and microbial parameters as influenced by catch crops and straw management

“…According to many researchers, mineralization and immobilization of incorporated organic matter are influenced by its chemical composition, especially C:N (Justes et al, 2009). In our study, the C:N in the above ground mass of various catch crops was favourable for decomposition and varied little depending upon the type of crops.…”

“…Incorporation of only catch crops' biomass led to N min increase by 6.31-9.90 mg kg -1 , meanwhile when straw had been spread -by 7.18-12.40 mg kg -1 of soil, compared to that in the autumn. N immobilization occurs only during a limited period of time, sufficient to prevent part of the mineral N pool from leaching, and net N mineralization can be expected during the subsequent cropping season, thus enhancing synchronization of N supply and demand (Trinsoutrot et al, 2000;Vinten at al., 2002;Justes et al, 2009). Another factor, which determines decomposition is soil properties, i.e.…”