Determination of an Integrated Compost and Phosphorus Management Strategy for Cowpea Production in the Wet Savannah Ecosystem of Nigeria

Abstract

The trial was conducted at two sites within the Wet Savannah zone of Kwara State, Nigeria. The primary objective was to promote cowpea as a major crop in this ecological region and to evaluate the effects of compost manure and phosphorus application on cowpea productivity. Compost was applied at a rate of 2.5 t ha⁻¹, while P₂O₅-only was applied at 50 kg ha⁻¹. Additional treatments included combinations of compost and P₂O₅, as well as a control group. The results demonstrated that the control and P₂O₅-only treatments yielded statistically similar outcomes for most growth and development parameters (p ≤ 0.05), both of which were inferior to the other treatments. This reduced performance was attributed to soil acidity. The number of days to 50% flowering decreased to 57.94, suggesting adaptation toward early maturity to avoid abrupt life cycle termination. The combined application of compost and P₂O₅ produced a synergistic effect (p ≤ 0.05), resulting in enhanced branching (9.71), leaf area (100.45 cm²), nodulation (45.47), and grain yield (1,081.20 kg/ha). These improvements were attributed to the synergistic interaction between compost manure and P₂O₅. It is therefore recommended that compost be applied at 2.5 t ha⁻¹, supplemented with P₂O₅ at 50 kg ha⁻¹, to optimize cowpea production in the Wet Savannah zone.