Effect of Phosphorus Fertiliser on the Yield of Cowpea in Borno State

This study examines the effect of different phosphorus fertiliser application rates on the growth and grain yield of cowpea in Borno State, North East Nigeria. Phosphorus deficiency is a primary soil fertility constraint for legume production in the sandy soils of the Lake Chad basin area of Borno State. Phosphorus is essential for nodulation, nitrogen fixation, root development, and seed formation in cowpea, and its deficiency severely limits yield potential even when rainfall is adequate. This study establishes a randomised complete block design experiment at the University of Maiduguri research farm, applying single superphosphate at five rates: 0, 20, 40, 60, and 80 kilograms of phosphorus pentoxide per hectare. IT90K-277-2 improved cowpea variety is used. Nodule number, nodule dry weight, plant height, number of pods per plant, grain weight, and grain yield are measured. Findings reveal that grain yield increases significantly up to 40 kilograms of phosphorus pentoxide per hectare, producing 1.6 tonnes per hectare compared to 0.7 tonnes per hectare in the unfertilised control. Nodule number and dry weight are maximised at 40 kilograms per hectare, demonstrating the critical role of phosphorus in nitrogen fixation. Beyond 60 kilograms per hectare, no significant yield increment is observed. The study concludes that 40 kilograms of phosphorus pentoxide per hectare is the economically optimal phosphorus rate for cowpea in Borno State. It recommends this rate for integration into the state ADP's cowpea production guidelines.

Keywords: phosphorus fertiliser, cowpea yield, Borno State, nodulation, soil fertility.