Mineralisation of C and N from root, stem and leaf residues in soil and role of their biochemical quality

The influence of biochemical characteristics of 15 crop residues on C and N mineralisation in soil was investigated by following the decomposition of roots, stems and leaves of four subtropical species and one temperate species buried into the soil. The C, N and poly-phenols contents were measured in different biochemical pools obtained from residues of the different organs. The mineralisation of root C was significantly lower than that of leaves and stems. Chemical analysis showed a higher polyphenol content in the leaves and a higher ligninlike content in the roots. Carbon and N mineralisation were simulated with the STICS decomposition submodel and tested against the data set. The model predicted leaf and stem C mineralisation for all five species fairly accurately, but failed to predict root C mineralisation, indirectly revealing the more complex composition of the root tissue. The results showed the interest of separately considering the different plant parts when studying plant residue de-composition and the need to develop other methods of residue quality characterisation to improve the prediction of residue decomposition. (Résumé d'auteur