Influence of Different Rates of Phosphorus and Potassium Fertilizer Application on Growth and Yield of Cowpea (Vigna unguiculata L. Walp) Varieties.

Abstract

The study evaluated the influence of rates of phosphorus (p) and potassium (k) fertilizers on the growth and yield of two cowpea varieties (IT0K-863-11) and ITOK-1228-14) for two consecutive seasons (2020 and 2021). Three/rates of p (0, 20, 30 kg/ha P2 O2) and four rates of K (0, 20, 30, 40,kg/ ha K2O) were utilized. The experimental design was 2x3x4 factorial arranged in randomized complete block replicated three times. Result indicated that leaf area index (LAI) at four weeks after sowing (4 WAS) in 2020 significantly (p<0.05) increased as p rates increased. However, at 10 and 12 WAS in 2020 and 2021 leaf area index (LAI) significantly (p<0.5) increase with 20 kg /ha P205 but reduced at 30 kg/ ha P2O5 application. In both cropping season, 30 and 40 kg /ha produced similar but highest LAI at 4, 8 and 10 WAS. Interaction of P and K demonstrated that at 4 WAS application of only 30 kg/ha K2O without P gave highest LAI (0.09 and 0.09) in both cropping seasons. All the yield parameters progressively increased as rates of K increased. Highest number of fresh pods/plant and seeds/pod, heaviest fresh pods per plant and as well as seed yield were associated with 40 kg /ha K2O application in both cropping seasons. The application of 40 kg /ha K2O with no application of P also produced better yield and yield attributes of the cowpea, hence 40 kg /ha K2O application without P was recommended for sustainable cowpea production in the Northern Guinea agro-ecological zone of Nigeria, especially when the soil has high available P (above the critical P level of 7mg/kg recommended for cowpea production).