Differential Responses of Cowpea (Vigna unguiculata) lines to phosphorus fertilizer in a low phosphorous Soil in the Southern Guinea Savanna Of Nigeria

Abstract

Fifteen cowpea (Vigna unguiculata) lines selected from a pot experiment for tolerance to low P were further evaluated for two years under field conditions for their response to low (0 kg Pha-1) and high (40kg pha-1) P fertilizer rates. The experiments were conducted within the Southern Guinea savanna ecological zone of Nigeria. The cowpea lines exhibited differential responses to phosphorus. The average range of N2 – fixed by the cowpea lines was 26-75% at low P, 32-74% at intermediate P and 30-70% at high P. Arbuscular mycorrhizal infection of cowpea roots were 11-28%, 12-22% and 11-22% at low, medium and high P rates, respectively. Based on their dry matter and grain yields with or without P application. The cowpea lines were classified into four groups. Group I (non responders) had low yield with or without P application.Group II (Tolerant) produced high yield without P and application group III (Sensitive) showed low yield without P and high yield with P application Group IV (responders) had high yield with or without P application. High dry matter production at low P was exhibited by six lines, while seven lines produced high grain yields. Cowpea line IT90k-284-2 consistently out performed other lines at low P, thus showing good prospects for both grain and fodder production in low P soils.

Nigerian Journal of Soil Science Vol. 17 2007: pp. 52-64