Response of special cowpea varieties to inorganic fertilizers in Ogbomoso, Nigeria

Abstract

Phosphorus is the most limiting nutrient element in cowpea production and productivity. Therefore, this experiment was aimed at  investigating the response of cowpea to inorganic fertilizer treatments (with soil macro nutrient elements) in Ogbomoso, a derived  savanna agro-ecological zone. Ten varieties of cowpea, sourced from IITA, were evaluated under five inorganic fertilizer treatments (phosphorus alone, phosphorus + nitrogen, phosphorus + potassium, phosphorus + nitrogen + potassium, control) using completely  randomized design with four replicates at the Teaching and Research Farm of Ladoke Akintola University of Technology, Ogbomoso, in  2019. Data were collected on date of germination, plant height and number of leaves. In addition, cowpea plant samples were prepared  and taken to IITA for nitrogen, phosphorus and potassium analyses. Also, dry matter, nitrogen, phosphorus and potassium uptake were  determined for the cowpea varieties. Data were subjected to analysis of variance and significantly different treatment means were  separated using Duncan‟s Multiple Range Test (DMRT) at the 5 and 1% probability levels. There were significant differences (p < 0.05)  among the cowpea varieties and the different inorganic fertilizers investigated. The interaction effects of the two factors were highly  significant for plant height, root nodules, nutrient uptake and concentration. The interaction between cowpea variety TVU 12138 with applied nitrogen, phosphorus and potassium fertilizer produced the highest fresh and dry root weight. In addition, the interaction  between cowpea variety TVU 7439 with applied nitrogen, phosphorus and  potassium combined gave the highest mean performance for  N and P uptake and concentration while cowpea variety TVU 17028 with applied phosphorus and potassium also gave the highest  average performance for N, P, K and NPK uptake and concentration. These interactions should further be investigated on cowpea yield in  future studies.