Parameterisation of the NCSOIL model to simulate C and N short-term mineralisation of exogenous organic matter in different soils

Abstract

The recycling of exogenous organic matter (EOM) through agriculture is an efficient way to enhance soil organic matter (SOM) and to supply crops with readily available nutrients. It can also cause environmental damage, such as nitrate leaching. Characterisation of EOM to predict the C and N dynamics of mineralisation when applied to cropped soils is essential to improve its use in agriculture. The measurement of C and N mineralisation through soil laboratory incubation of 18 types of EOM and EOM biochemical fractionation were used to parameterise the NCSOIL model to simulate the mineralisation kinetics of C and N. The soil type did not significantly interfere with EOM mineralisation and parameterisation, enabling extrapolation of the parameters for one soil to other soil types. Four groups of EOM were distinguished based on their C and N dynamics: (1) stable compost, (2) more reactive compost and stable manure, (3) manure and (4) very reactive EOM as sludge and litter that should be used as fertiliser. The use of easily accessible indicators, such as IROC (Lashermes et al., 2009) and the measured organic C:N ratio (CNEOM), was appropriate for parameterising groups 1 and 4. Regression relating the optimised resistant pool size and Van Soest fractions and CNEOM was found (R2 of 0.967) to improve the pool sizes for the remaining EOM. Further research is required to improve the parameterisation.