Growth and yield responses of cowpea genotypes to soluble and rock P fertilizers on acid, highly weathered soil from humid tropical West Africa

Abstract

Soils in tropical regions have inadequate levels of phosphorus and this apparently leads to reduced cowpea yield in Africa. Identifying phosphorus-efficient cultivars have the potential to reduce the demand for phosphorus fertilizer and increase the productivity of cowpea. This study was conducted to identify cowpea genotypes that maintain high yields under low soil phosphorus condition. A green-house experiment was conducted at the International Institute of Tropical Agriculture, Ibadan, Nigeria. Fifteen cowpea genotypes were used with two sources of phosphorus fertilisers: rock phosphate (60, 90 and 120 mg P kg⁻¹ soil) and mono potassium phosphate (30, 60 and 90 mg P kg⁻¹ soil) and compared to the control. The experiment was laid out in a strip plot arrangement with three replications. The findings suggested that large geneticvariability exist among the tested cowpea genotypes. IT90K-59 was identified as best phosphorus responder genotype for biomass production and IT90K-76 for grain yield at a rate of 60 mg P kg−1 soil as mono potassium phosphate. Danila and IT89KD-288 were identified as promising genotypes under no or minimal external P application. Five genotypes were identified as good responders to rock phosphate based on their grain yield production. The differential response of the genotypes to low soil phosphorus implies that these traits warrant effective selection for further improvement. Thus, identifying genotypes that can grow well in low phosphorus condition has the potential to reduce the quantity of mineral fertilizersand cost of production.

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Keywords: Rock phosphate, mono potassium phosphate, Alfisol soil