Effect of phosphorus fertilizer application on the growth traits and grain yield of cowpea

Abstract

Phosphorus is one of the major essential nutrient elements required in adequate quantity in available form for proper growth and development of crops. However, phosphorus is one of the most limiting nutrient elements in tropical soils for the production of various crops, especially leguminous crops. This study was carried out at Makerere University Agricultural Research Institute Kabanyolo (MUARIK) to determine the effect of phosphorus fertilizer on the growth and yield performance of cowpea. The experimental design was a randomized complete block design with three replications. The treatments comprised a control where phosphorus fertilizer was not applied, 20, 40, and 60 kg P/ha. Data were collected on growth traits namely, number of leaves per plant, number of branches per plant, number of root nodules, plant height, fresh weight of the root, and fresh weight of the aboveground biomass, as well as yield performance traits, namely the number of pods per plant, number of seeds per pod, pod length, the weight of 100 grains per plot and grain yield per plot. The results showed that the gradual increase in phosphorus fertilizer application resulted in a gradual increase in plant height and several branches, with the rate of 40 kg P/ha giving significant (P<0.05) increases in plant height and number of branches when compared with the control. The number of root nodules and the above-ground biomass increased gradually, becoming significantly (P<0.05) higher than in the control at the application rate of 60 kg P/ha. The phosphorus application rate of 40 kg P/ha produced a significantly higher number of pods per plant and the number of seeds per pod when compared with the control. Grain yield increased with a gradual increase in P levels, and the rates of 40 and 60 kg P/ha produced significantly higher grain yields than the control. Based on the results, it was concluded that the application of phosphorus fertilizer at the rate of 40 kg/ha is suitable for optimum growth and grain production of cowpea. It was recommended that farmers growing cowpea should apply phosphorus fertilizer at the rate of 40 kg/ha and above to obtain significant increases in cowpea grain yields. However, further research should be conducted using higher application rates of phosphorus fertilizer to determine the rate of application that would optimize the grain yields of cowpea.