Modelling the mineralisation of plant residues on the soil surface

A general assumption in many agroecosystem C and N turnover models is that the decomposition of added organic matter starts at the moment of residue incorporation into the soil. In fact, decomposition is already initiated on the surface of the soil. This decomposition of surface crop residues has been modelled mainly to describe the decrease in soil cover which protects the soil surface from erosive forces, but not to simulate change in surface crop residue quality and mineralisation of C and N. Therefore, we included a surface decomposition submodel in an existing mineralisation model and tested the new C and N turnover model using data from a field site study. The results show that the new model is able to describe the C and N turnover of crop residues in more detail, including the decrease of soil cover observed in the field.