Modelling long-term effects of crop residue management for sustainable farming systems

Abstract

Field research has shown a significant yield increase with the use of millet crop residues (CR) as a soil mulch. The short-term profitability of this management practice is, however, low. This paper examines the long-term effects of mulching on soil fertility, the decreasing accessibility of fallow and, consequently, the reduction in the opportunity of restoring the soil fertility through a fallow using a multi-period dynamic linear programming model. Depending on an assumed discounting rate for future incomes, the long-term evaluation indicates that a mulch application can be economically profitable compared to the tested alternative uses such as mulching at lower rates and the trade of stover. Four scenarios were analysed which focused on different land : labour ratios, discount rates, prices of CR, and a specific combination of mulch and working capital. The importance of fallow for long-term fertility management is shown, as well as the importance of a mulch application with millet stover in the absence of sufficient fallow. The optimal combination of fallow, and stover producing and consuming activities to master the mulch shortage, are presented. However, all scenarios show that with CR mulching alone, future soil degradation cannot be prevented.