Modifications made were: i) the minimum value of the rate modifying factor for moisture was changed from 0.2 to 0.15 and 0.10 (indicated with the suffix 20, 15 and 10, respectively, in the name of the model); ii) the maximum soil moisture deficit was increased and the hydrological constants (field capacity, wilting point and hygroscopic water) were calculated using pedotransfer function by (RothC20, RothC15, and RothC10); and iii) soils that were bare were allowed to dry out more than in the current version of RothC (RothC_N, RothC20_N, RothC15_N, and RothC10_N).
The modifications were tested on data from six experiments: five sites from semiarid regions and one from a temperate region.
The modifications made in this study, which essentially reduce decomposition rate in soil, improved the model's performance for dry regions, especially when the rotation included a fallow. The model now requires more realistic C inputs to the soil, and one additional input (silt) that is normally measured with clay. These modifications do not impair the performance of the model under temperate conditions and so represent a broadening in the capability of the RothC model. Among all the various models compared, for simulation of SOC turnover we suggest the use of RothC10_N for dry regions as a part of global scale modelling.