Cowpea yield under the influence of cropping system, location and nitrogen fertilization

Yield production of cowpea depends largely on the environmental factors, cropping systems and soil type of the location. In this way, an experiment was conducted to investigate the interaction effect of cropping system, location, season and nitrogen fertilization on cowpea yield. The study comprised of three cropping systems (Maize-cowpea rotation, monocropping cowpea and intercropped cowpea), three locations (Potchefstroom, Taung, and Rustenburg, South Africa) and two rates of nitrogen fertilizers applied in kg ha⁻¹ at each site (0 and 20 at Potchefstroom, 0 and 17 at Rustenburg, 0 and 23 at Taung). A factorial experiment randomized in complete block design with three replications was conducted during 2011/12 and 2012/13 planting seasons. The measured yield and yield components were pod length, seed per pod, pods mass at harvest, grain yield and field biomass yield. Cowpea planted on monocropping and rotational systems had significantly (P < 0.05) higher seed number per pod at harvest, grain yield and field biomass yield than cowpea planted on intercropping. The interaction of location x season plays a vital role on cowpea production by increasing yield. A single cultivar might differ significantly across different locations due to different soil types and climatic factors.