Study of Crop Rotation Benefits for Soil Nitrogen and Sorghum Productivity in Katsina State

Crop rotation involving legumes improves soil nitrogen status and reduces pest and disease pressure on subsequent cereal crops, and documenting these benefits under smallholder conditions in the Sudan savanna of Katsina State generates evidence to support adoption of rotation-based cropping systems. This study investigated the effects of three preceding crop treatments (bare fallow, sole cowpea, and sole groundnut) on residual soil nitrogen and subsequent sorghum grain yield in Dutsin-Ma LGA, Katsina State, North West Nigeria. A two-season field experiment was conducted in 2022 (legume-fallow season) and 2023 (sorghum season) using a randomised complete block design with three replications. Soil total nitrogen was analysed after the legume season and at sorghum harvest. Sorghum plant height, tiller number, panicle weight, and grain yield were recorded. Results showed that plots previously under cowpea had significantly higher soil nitrogen (0.14 percent) than fallow (0.09 percent) and groundnut (0.12 percent) plots before sorghum planting. Sorghum grain yield was highest following cowpea (2.87 t ha-1) and groundnut (2.71 t ha-1) compared to fallow (2.09 t ha-1). Nitrogen equivalence calculation showed that cowpea preceded sorghum providing the equivalent of 34 kg N ha-1. The study concludes that cowpea-sorghum rotation is the most nitrogen-beneficial rotation for the study area and recommends its inclusion in Katsina State ADP cropping system advisory packages.

Keywords: crop rotation, soil nitrogen, sorghum productivity, cowpea-sorghum, Katsina State