Effect of irrigation on phenology, growth and yield of cowpea (Vigna unguiculata)

The response of cowpea to supplemental irrigation at various growth stages was compared with a rainfed and a full irrigation (no stress) treatments during rainy season of 1992 and 1993 at Coimbatore. Withholding irrigation at flowering and pod filling stages of crop enhanced the process of maturity. Among the yield components pod density was most sensitive to irrigation. Crop without water stress in any part of the plant growth recorded four times higher yield (8.69 q/ha) than rainfed treatment (2.19 q/ha). Supplemental irrigation during flowering and vegetative stages alone increased the seed yield by 94% (4.24 q/ha) and 75% (3.84 q/ha), respectively, over the rainfed crop. Two irrigations given either at flowering and pod filing stages or vegetative and flowering stages increased seed yield by 172% and 160% in comparison to rainfed treatment respectively. Irrigations at vegetative, flowering and pod filling stages produced comparable yields as that of full irrigation treatment. Supplemental irrigation only at flowering stage recorded maximum water use efficiency (155 kg DMP/ha/mm).