Water Requirement of Some Crops Grown under Shallow Perched Water-Table at Indira Gandhi Canal Command, Western Rajasthan

Reference crop evapotranspiration (ET_o), water reqnirements (ET_o) and net irrigation requirements (NIR) of kharif and rabi crops grown under shallow water-table in Lunkaransar area of Indira Gandhi Canal Command were estimated using Modified Penman (Mo-Pen) and pan evaporation methods. Estimates of ET_o by both the methods were of similar magnitude, the correlation coefficients being highly significant (r= 0.87, 0.95 and 0.88 during kharif, rabi and summer seasons, respectively). Estimates of water requirements by the two methods followed the order: pigeonpea (503 mm in each) > pearl millet (488 and 491 mm) > groundnut (430 and 452 mm) for kharif and gram (239 and 260 mm) > wheat (213 and 227 mm) > mustard (129 and 142 mm) for rabi crops. Phenophasic differences in ET_o, of crops existed with peak values during flowering, pod development/grain filling stages of the crops. The ground water-table contribution (GWC) varied from about 79 to 98 mm in kharif crops and from 71 to 113 mm in rabi crops. When GWC was accounted for, the net irrigation requirements were reduced by 12.7 to 34.9 per cent. The results demonstrate the potential use of simple pan evaporation method for estimating crop water requirements of canal command areas where detailed meterological data are not available.