Influence of soil moisture content and fertilizer potassium on the growth of cowpea (Vigna unguiculata) in sandy regosol

Abstract

Cowpea is grown in a wide range of environments, and drought is considered as the single most devastating environmental stress, which decreases crop productivity more than any other environmental stress. Lack of adequate soil moisture affects both the vegetative and reproductive growth of legumes and leads to significant yield loss. Potassium fertilizer mitigates the impact of water stress in plants. A study was conducted from July to September 2018 to investigate the effect of four rates of fertilizer potassium (MOP) including recommended level (75Kg/ha), 125% of recommended level, 150% of recommended level, 175% of recommended level with two different soil moisture conditions as optimal and suboptimal on growth of cowpea. These 8 treatments replicated three times in a Completely Randomized Design (CRD) in a factorial manner. Growth parameters of cowpea were recorded. The data were statistically analyzed using SAS and difference between treatment means was compared using Duncan’s Multiple Range Test (DMRT). The tap root length of cowpea showed a greater response to potassium fertilizer under suboptimal soil moisture. Although differences were observed in the responses of the vegetative growth of cowpea to moisture and potassium, in overall terms potassium promoted growth of cowpea when subject to suboptimal soil moisture. Among all applications 175% of recommended potassium level of cowpea proved to be the best to increase the shoot dry weight and leaf area at optimal moisture conditions, and under sub-optimal moisture conditions it was the best to increase the shoot dry weight and leaf area compared to recommended level of potassium in sandy regosol soil. The results of this study suggested that the application of potassium fertilizer can be considered as significant factor in overcoming soil moisture stress in cowpea.