Agronomic Responses to Four Tillage Variants on a Sandy-loam Ultisol cropped to Sorghum and Soybean in the derived Savanna of Southeastern Nigeria

The study evaluated the effects of no-till (NT) and conventional tillage (CT) left bare (B) or mulched (M) giving four treatments; NTB, NTM, CTB and CTM) on profile moisture storage, grain yield and carbon storage under sole- and intercropped sorghum and soybean in 2006 and 2007 growing seasons. In the sole sorghum, NTB and CTM enhanced moisture storage over NTM and CTB. The grain yield was lower in CTB than the other treatments. In the sole soybean, NTM and CTM enhanced moisture storage over NTB and CTB, but the differences in grain yield were consistently non-significant. In the intercropped field, moisture storage differed such that CTM > NTB > NTM = CTB. Whereas grain yield of the sorghum component followed suit, that of the soybean component remained uninfluenced. Overall, the differences in sorghum yields among the tillage methods were less pronounced in the first compared to the second year – when rainfall distribution was relatively erratic. The treatment-induced moisture explained over 60 and 72% of the variability in grain yield of the intercropped sorghum in the first and second year, respectively. In this short-term study, the CTB had the least carbon storage potential in the three cropping systems for which differences tended to be sole sorghum ≤ sole soybean ≤ intercrop. The NTB, NTM/NTB and CTM/NTB are recommended for growing sorghum, soybean and their intercrop, respectively.