Low input approaches for soil fertility management in semiarid eastern Uganda

Grain sorghum [Sorghum bicolor (L.) Moench] is an important food crop of semiarid sub-Saharan Africa. Crop yields are generally low, partly due to low soil fertility. Research was conducted with farmers to evaluate, soil fertility management practices in sorghum-based cropping systems including: mucuna [Mucuna pruriens (L.) DC.] fallow; cowpea [Vigna unguiculata (L.) Walp.] rotation with sorghum; animal manure application; N and P fertilizer application; and reduced tillage. Four studies, comprised of 142 on-farm trials, were conducted at three locations over 3 yr in drought-prone parts of eastern Uganda. Mucuna on average produced 7 Mg ha(-1) of aboveground dry matter containing 160 kg N ha(-1) across the three locations. Application of 2.5 Mg ha(-1) of manure and of 30 kg N plus 10 kg P ha(-1) increased grain yield by 1.05 and 1.30 Mg ha(-1) respectively. A combination of 2.5 Mg ha(-1) manure with 30 kg N ha(-1) increased grain yield by 1.50 Mg ha(-1) above the control (1.1 Mg ha(-1)). The increase in sorghum grain yield in response to 30 kg N ha(-1) alone, to a mucuna fallow, and to a rotation with cowpea was 1.15, 1.55, and 0.82 Mg ha(-1), respectively. These soil fertility management practices, as well as reduced tillage, were found to be cost effective in increasing sorghum yield in the predominantly smallholder agriculture where inorganic fertilizer was not used much. On-farm profitability and food security for sorghum production systems can be improved by use of inorganic fertilizers, manure, mucuna fallow, sorghum-cowpea rotation, and reduced tillage.