Water Use Efficiency of Selected Cowpea Cultivars (Vigna unguiculata (L.) Walp) Grown on Residual Soil Moisture in Northeast Nigeria

A field experiment was carried out in the Fadama of Jere bowl to assess the water extraction and water use efficiency of two improved (IT 86D-719 and IT88D-867-11) and one local (Borno Brown ) cowpea cultivars grown on residual soil moisture. The three cowpea cultivars and a control were laid out in a randomized complete block design and replicated three times. The result showed that yield and growth parameters were significantly (P< 0.05) different amongst the three cowpea cultivars. The improved cultivars gave significantly (P< 0.05) higher seed yields than the local cultivar. Cultivar IT 86D-719 had the highest seed yield of 893.0 kg ha-1 while the cultivar Borno Brown had the lowest seed yield of 675.3 kg ha-1. On the other hand the cultivar Borno Brown had the highest 100 seed weight compared to the improved cultivars. The result also showed that water extraction in all the cultivars increased with depth, with maximum extraction occurring at the depth of 80-100 cm, suggesting that the lower soil layers were more effective in supplying water as the hydraulic conductivities of surface layers decreased. The water use efficiency of the two improved varieties of IT86D-719 (63.56 kg/m3) and IT88D-867-11(70.06 kg/m3), were higher compared to the local variety (45.69 kg/m3). Borno brown and IT 88D-867-11 are good water extractors at field capacity but low extractors at moisture stress. IT 88D-867-11 displayed sign of higher extraction rate than IT 86D-719 at field capacity, but IT86D-719 displayed a higher extraction capacity at moisture stress (20WAS).