EFFECT OF PHOSPHOROUS RATES ON GROWTH AND YIELD OF COWPEA [Vigna unguiculata (L.) Walph.] VARIETIES IN JOS NORTH, PLATEAU STATE, NIGERIA

Abstract

The study was conducted in Jos North, Plateau State, Nigeria to determine the effect of phosphorous rates on the growth and yield of cowpea varieties during the 2017 and 2018 growing seasons. The study consisted of four phosphorous rates (0, 20, 40 and 60 kg P₂O₅ ha^-1) and three cowpea varieties (IT93K-452-1, IT99K-499-35 and IT90K-277-2) factorially combined and laid out in a Randomized Complete Block Design (RCBD) replicated three times. Data collected were subjected to analysis of variance (ANOVA) using XLSTAT 2019 statistical package and Duncan Multiple Range Test (DMRT) was used to separate the means where significance was declared. The result showed that application of 60 kg P₂O₅ ha^-1 recorded the tallest plant height (40.60 and 41.11 cm), a greater number of leaves (59.11 and 60.22), higher number of seeds per pod (12.00 and 11.67), least number of days (36.78) to attain 50% flowering. The highest number of branches (15.89 and 15.78), larger leaf area (115.91 and 117.63 cm²), a greater number of pods per plant (56.78), higher total yield (1.88 tha^-1) was obtained at application of 40 kg P₂O₅ha^-1. Similarly, varietal differences were highly significant (P≤0.01) on growth and yield of cowpea. IT93K-452-1 variety produced the tallest plant (38.37 and 38.97 cm), more leaves per plant (55.75 and 57.08), more branches per plant (15.25 and15.28), larger leaves (112.78 and 113.35 cm²), more pods per plant (54.50 and 53.67), higher number seeds per pod (11.08 and 11.58), higher yield (1.82 and 1.88 tha^-1) and the least number of days to reach 50% flowering. The interaction of phosphorous and variety was highly significant (P≤0.01) with IT93K – 452 – 1 showing greater response to the application of 40 kg P₂O₅ ha ^-1 on yield of cowpea. In conclusion, application of 40 kg P₂O₅ ha^-1 was the best rate for good growth and yield of cowpea. Higher growth and yield characters were consistently measured for IT93K-452-1 variety. It is recommended that farmers in the study area can apply 40 kg P₂O₅ ha^-1 to IT93K – 452 – 1 variety to enhance the productivity of cowpea.