Effects of phosphorus and zinc levels on total soluble carbohydrate and crude protein in grain of cowpea (Vigna unguiculata (L.) Walp) grown in Bauchi, Nigeria

Abstract

Two field experiments were conducted at the Faculty of Agriculture and Agricultural Engineering Research Farm of Abubakar Tafawa Balewa University, Bauchi, between 2006 and 2007 to study the effects of phosphorus (0, 25, 50 kg P/ha) and zinc levels (0, 2.5, 5 kg Zn/ha) on Total Soluble Carbohydrate and Crude Protein of six cowpea varieties namely: IT90K 277, IT93455 1, IT89KD 288, IT97K 568 18, IT90K 82 2 and Kanannado. The objectives of these experiments were to determine which levels of P, Zn and the various interactions of P, Zn, and year that had produced the highest total soluble carbohydrate (TSC) and crude protein (CP) on the grain contents of the cowpea varieties studied and to determine the best varieties in terms of TSC and CP upon the application of these nutrients (P and Zn) in Bauchi, Nigeria. The results revealed that increased levels of P from P0 to P50 significantly increased the CP and TSC contents of the cowpea grains. Similarly, higher Zn levels (2.5 and 5 kgha-1) were observed to have significant effects on TSC and CP contents of the cowpea grains. Interactions of P and Zn were equally observed to significantly affect TSC and CP contents of the cowpea grains. Of all the six (6) cowpea varieties, Kanannado recorded the highest TSC and CP in the cowpea grains. With regard to year, 2006 recorded the highest CP while 2007 had the highest TSC. Higher levels of P and Zn or their associations were recommended for improving TSC and CP contents of the cowpea grains, with emphasis on Kanannado for Bauchi farmers.