Crop residue and integrated soil fertility management in mixed crop-livestock systems: A case-study in Southern Mali

Abstract

In Southern Mali, a debate needs to be engaged within farmer communities to solve the problem of crop residue management in order to satisfy both farm animal feeding and soil fertility maintenance. The aim of this study was to simulate the behaviour of the stable soil carbon (SSC) component at the farm and village levels. We chose specific critical soil carbon levels at 0 to 20 cm depth to be maintained during theoretical permanent cultivation. We quantified the production, the use and the residue behaviour of the main four crops in each of three villages and on 10 representative farms. Yearly SSC balances carried out at the farm level with the most common scenario according to recorded farmers' practices, i.e. stable organic carbon coming from soil incorporation by tillage of 25% of total bovine faeces associated with some decomposed crop residues and remaining field crop residues at the end of the dry season, revealed a strong topsoil SSC deficit at the farm level. In the three villages a scenario which simulated an increase of residue biomass, associated in two of the three villages by stopping the crop residue burning and doubling total bovine faeces incorporated into the soil, would provide sufficient SSC balances for the large majority of farms without any change relating to bovine free-grazing during the dry season. This original approach which links farmers' practices to field SSC balances at both farm and village levels could be used in other situations in Southern Mali and in other mixed-farming contexts where soil fertility maintenance is questionable.