Grain Sorghum Response to Reduced Tillage, Rotation, and Soil Fertility Management in Uganda

Grain sorghum [ Sorghum bicolor (L.) Moench] is an important staple crop in Uganda, but its productivity is limited by numerous constraints. Practices including reduced tillage (RT), conventional tillage (CT), sorghum rotation with mucuna ( Mucuna pruriens L.) and cowpea ( Vigna unguiculata L.), and soil fertility management treatments (SFTs) were evaluated to determine their effects on grain yield over a 7‐yr period with two cropping seasons per year at Bulegeni and IkiIki representing high and low potential agroecological zones, respectively. At Bulegeni and IkiIki, respectively, mean grain yield was 13.0 and 8.6% greater with RT compared with CT, 10.9 and 14.4% greater following mucuna compared with cowpea, and 134 and 249% greater with farmyard manure (FYM)+N+P compared with no nutrient applied. At Bulegeni, SFT effects on sorghum yields increased with time. Factor interactions occurred, but grain yield was greatest due mainly to additive effects with a combination of RT, mucuna as the previous crop, and FYM+N+P. The SFTs accounted for >70% of the variation in annual treatment means for grain yield. Trial mean grain and stover yields were less for Years 1 through 4 compared with Years 5 through 7, especially at Bulegeni and with FYM and/or fertilizer application. Factor interaction effects on some soil chemical properties were inconsistent across locations. Mucuna rather than cowpea as the rotation crop, RT rather than CT with an increasing RT benefit over time, and nutrient application can be used alone or additively to increase sorghum grain yield, but positive factor interactions were inconsistent and accounted for little yield increase. Sorghum grain yield was increased by additive effects of nutrient application, reduced tillage, and rotation. Synergistic effects of combining two or more practices were small and uncommon. Sorghum yield was greatly increased by nutrient application. Farmers can benefit from adopting any of the more beneficial practices alone or in combination.