Evapo-transpiration, water and radiation-utilization of clusterbean (Cyamopsis tetragonoloba)

The evapotranspiration rate of unstressed 'Maruguar' clusterbean (Cyamposis tetragonoloba (L.) Taubert) in an arid region at Jodhpur was 2.4-3.9 mm/da y during early growth, 6.3-9.3 mm/day at peak vegetative stage, 5.3-5.8 mm/ day at flowering/pod formation stage and 1.2-4.2 mm/day at maturity stage. The crop coefficient (ratio of actual to potential evapotranspiration) was 0.42-0.58 at early growth stage, 0.62-1.17 at peak vegetative stage, 0.70-1 .05 flowering and pod formation stages and declined to 0.43-0.60 at maturit y. Irrigation enhanced seed yield of clusterbean by 123% at 50% rate and 18 0% at 100% rate of water application from that of rainfed crop. Ther water- use efficiency of the crop varied from 1.47 to 4.10 kg/ha/mm and the radiat ion-use efficiency for unit dry matter production of intercepted photosynth etically active radiation was 0.57-1.21 g/MJ under rainfed to 1.42-2.31 g/M J under irrigated condition. Advection enhanced evapotranspiration of clust erbean by 50-78%.