PRODUCTIVITY OF COWPEA AS INFLUENCED BY BRADYRHIZOBIAL STRAINS AND PHOSPHORUS LEVELS IN THE SUDAN SAVANNA OF NIGERIA.

Field trials were conducted during the 2015 wet season at the Bayero University, Kano (BUK) Teaching and Research Farm (11 0 58’N, 8 0 25’E and 475 m above sea level) and National Institute of Horticultural (NIHORT) Bagauda (Lat. 12 0 08'N, Long. 8 0 32'E, 500 m above sea level). The study was conducted to determine the response of cowpea ( Vigna unguiculata L. Walp) varieties to rhizobium and phosphorus levels in the Sudan Savannah of Nigeria. The treatments consisted of four cowpea varieties (UAM-09-1051-1, IT99K-573-2-1, IT99K-573-1-1, and TVX 3236), rhizobium (0, and 100 g ha -1 ) and phosphorus (SSP) (0, 20, and 40 kg/ha) laid out in a Split Plot Design. Phosphorus and Bradyrhizobium were allocated to the sub plot while variety was allotted to the main plot. Application of 40 P 2 O 5 kg/harecorded the highest grain yield ha -1 at BUK. Bradyrhizobium spp. inoculation on cowpea recorded a consistent result across the two locations. Significantly, higher 100-seed weight was recorded at Bagauda and BUK, respectively. Significantly higher grain yield was observed from inoculated plants at BUK (1007.22 kgha -1 ) and Bagauda (719.910 kg ha -1 ). The findings of the study revealed that there was significant varietal effect on cowpea growth and yield at both study locations. Variety IT99k-573-2-1 gave higher yield (1193.400 kgha -1 ), followed by variety TVX 3236 (950.90 kgha -1 ) and IT99k-573-1-1 (776.50 kgha -1 ) at BUK. Significant interactions in respect of phosphorus and rhizobium were also recorded on the grain yield. Based on the result of the study, application of 40 P 2 O 5 kg/ha and variety IT99k-573-2-1 could be recommended for better cowpea growth and yield.