Yield and yield components of cowpea (Vigna unguiculata (L.) Walp.) as influenced by Sokoto phosphate rock and placement methods in the semi-arid zone of Nigeria

Abstract

Phosphate rock with proper management could be a sustainable source of phosphorus for increased cowpea production on the Entisols of Sokoto Semi-arid zone. Therefore, field experiments were conducted in 2004 and 2005 rainy seasons to determine the influence of Sokoto phosphate rock (SPR) and placement methods on the yield of cowpea varieties. Treatments consisted of factorial combination of two varieties (Ba’adare and IAR48), three levels of SPR (25, 50 and 75 kg SPR ha−1) along with a control (0 kg SPR ha−1) and three placement methods (plough sole, broadcast and side-band) laid out in a randomized complete block design replicated 3 times. Results of phosphate rock and placement methods are presented in this paper. The study indicated significant (P < 0.01) response to applied SPR compared to control (1074 kg grain ha−1) in most parameters studied. Application of 25 kg SPR ha−1 significantly (P < 0.05) influenced higher pod yield and number of pods plant−1 only in 2004 trial. But, shelling percentage, grain yield, stover yield, 1000-grain weight, harvest index (HI) and number of seeds pods−1 were not influenced by SPR levels. Significantly (P < 0.05) higher pod yield in 2004, grain yield, 1000-grain weight and number of pods per plant in 2004 and 2005, HI, shelling percentage and number of seeds pod−1 in 2005, were observed in plough-sole than broadcast and band-side methods of fertilizer placement. Therefore, from this study, it was concluded that SPR could be directly used as a source of P to sustain cowpea production (1527 kg grain ha−1 with 25 kg SPR compared to 1074 kg ha−1with 0 kg SPR). Application of 25 kg SPR ha−1 (3.74 kg P ha−1) using plough-sole method of fertilizer placement was most efficient under Sokoto semi-arid condition.