Soil fertility is now unanimously recognized as the major biophysical constraint of smallholder farms in sub-Saharan Africa. As low-input farming system, improving the efficiency of the locally available organic resources is one realistic strategy that farmers may follow to replenish soil nutrients. Manure represents an important linkage between livestock and soil productivity and constitutes the most common organic input available in significant amounts. During the rainy seasons, quantity and quality of grasses from the grazing area are determinants of livestock productivity and hence for manure production. During the dry season, shortages of palatable grasses make the crop residues key for cattle productivity.
This study aimed at describing and exploring the factors driving animal and crop residues mediated nutrient transfers for the case of smallholder farming system of the Manjonjo village in the Murewa district, Zimbabwe. Add to questions related to nutrient transfers at farm scale, the NUANCES-LIVSIM model was implemented with a feeding routine and tested for Zimbabwean situation.
Cattle feed production through crop residues from fields and grasses from grazing area were quantified within the village of Manjonjo. Practices and strategy were characterized based on interviews to get insight into assets and production constraints faced by farmers. The modelling framework developed in the project AfricaNUANCES and more specifically the animal production simulator LIVSIM was used to answer questions dealing with nutrient transfers in smallholder farming system related to cattle and crop residues management.
The cattle number was shown as the first factor which determines the concentration of nutrients from the grazing area and crop fields to kraal (0.06 g N kg-1 BW day-1). While grazing crop residues during the dry season, cattle export nutrients from crop fields (0.16 g N kg-1 BW day-1) at the expense of crop farmers. The combined effects of animal and crop residue managements are at the origin of an unequal redistribution of the nutrient pool contained within crop residues between cattle and crop farms.
Aiming at improving the livelihood of all farmers in the village, proposed technology must consider interaction between farmers particularly during the dry seasons. The modelling approach and LIVSIM have proved to be efficient in answering question dealing with nutrient transfers in smallholder farming system.