Productivity and Chemical Composition of Maize Stover and Rice Straw Under Smallholder Farming Systems Intensification in Tanzania

Cereal crop-dairy production is one of the crop-livestock production systems with a high potential for increasing food security of smallholder farmers in Africa. The question is how to meet the challenge of increasing the productivity and production efficiency of crops and milk per unit land area in highly populated areas of Tanzania. In these areas, smallholder farmers own an average of 0.5–2 ha of land and use the bulk of crop residues to feed livestock. This 4-year study aimed at demonstrating the impact of intensification, through improved plant nutrition, on productivity and chemical composition of maize and rice crop residues. The demonstrated treatments were farmers’ practice (FP) and improved plant nutrition (IPN). We recorded the yield of maize and rice crop residues and the concentration of macro- and micro-minerals in oven-dried samples of crop residue. The concentrations of N, P, K, Mg and Ca, which were not significantly (P > 0.05) different between the farmers’ and improved plant nutrition practices, ranged from 0.48% to 0.83%, 0.03% to 0.08%, 1.11% to 2.23%, 0.07% to 0.083% and 0.10% to 0.26% for maize stover and 0.48% to 0.84%, 0.08% to 0.23%, 2.31% to 2.83%, 0.20% to 0.33% and 0.10% to 0.22% for rice straw, respectively. The concentrations of Cu and Zn ranged from 2.3 to 14.0 and 6.0 to 20.5 mg/kg for maize stover and 1.7 to 12.4 and 27.0 to 55.7 mg/kg for rice straw, respectively. Comparable nutrients in the two agronomic practices can be related to nutrient dilution under improved plant nutrition due to high biomass production that was significantly (P 0.0.5) from those of the farmers’ practice in terms of nutrient concentration, we concluded that farmers’ practice crop residues obtained their nutrients mainly from soil reserve. Therefore, soil fertility mining happens when farmers feed all crop residues to livestock without the return of manure to the farm. The smallholder farmers, therefore, should be trained on the improvement of plant nutrition and feeding of crop residues to reduce depletion of soil fertility. Except for Zn concentrations, all other mineral concentrations and nitrogen content were low to very low for dairy cattle fodder, and supplementations of nitrogen and mineral premix are important in optimising milk production in cereal crop residue-based diets.