Quantification of water productivity and economics of irrigation in summer clusterbean (Cyamopsis tetragonoloba) in hot arid region of India

Abstract

Clusterbean [Cyamopsis tetragonoloba (L.) Taub, cv. RGC 936] is generally grown in arid parts of India and requires about 650 mm water during its crop growth period. Keeping in mind the water scarcity in future, performance of this crop has been assessed under different irrigation levels at the experimental farm of ICAR−Central Arid Zone Research Institute (ICAR−CAZRI), Jodhpur during summer season of 2015, 2016 and 2017. For this purpose, a specially developed mini−lysimeter was used with a dimension of 0.50 m × 0.50 m × 0.55 m. The measurement resolution of the mini−lysimeter was 0.2 mm equivalent soil moisture depth. Four levels of irrigations were applied in the experiment: 100%, 80%, 60% and 40% of cumulative pan evaporation (CPE) of 50 mm. It was observed that deficit irrigation levels resulted in decrease of crop evapotranspiration (ET ) by 19%, 34% and 50% under irrigation levels of 80%, c 60% and 40% of CPW, respectively over control (irrigation = 100% CPE). However, the corresponding reductions in yield were 10%, 48% and 67%, respectively. Water productivity was found highest, 0.35 kg m−3, at the irrigation level of 80% CPE. Further the economics of irrigation water application was computed to show the benefits of deficit irrigation apart from improving water productivity. It was found that for 1 ha−mm irrigation in the experimental field, it costs about ` 28.6. From this study, it may be inferred that by adopting 20% deficit irrigation level in summer clusterbean both physical water productivity and economic water productivity can be improved.