IRRIGATION METHOD AND WATER QUANTITY EFFECTS ON SWEET CORN

Soil evaporation, water use, yield of sweet corn (Zea mays L.) and wat er use efficiency as affected by two irrigation methods (trickle and s prinkler) and four values of irrigation water were studied in field pl ot experiments during 1991 and 1992 in the Jordan Valley. Irrigation r egimes were imposed on ? clay soil via line source sprinkler irrigatio n and trickle irrigation in three replicates. Four increasing amounts of water (W1, W2, W3, and W4) were applied twice a week with W3 adjust ed to compensate for evaporation measured by class A pan on the site. Soil water content was measured lust before each irrigation event at 1 50 mm increments starting at a depth of 75 mm using a neutron meter. W ith deficit irrigation and during incomplete canopy cover, the trickle irrigation method resulted in a substantial water saving owing to the small area of wetted ground surface compared with complete wetting of the ground surface with sprinkler irrigation method. Soil evaporation (E(s)) under sprinkler irrigation was significantly higher than E(s) under trickle irrigation method, whilst water use (WU) with sprinkler irrigation was slightly higher than WU with trickle irrigation at the same water level. With the lower irrigation water amounts (less than W 3), trickle irrigated sweet corn yielded better than sprinkle irrigate d sweet corn. However, sweet corn yields became comparable at excess i rrigation for both trickle and sprinkler irrigation methods, because e xcess water compensated for the adverse effect of soil evaporation. Al so, water use efficiency (WUE) with trickle irrigation was higher than WUE with sprinkler irrigation, and the maximum WUE occurred at 366 an d 410 mm water use for both trickle and sprinkler irrigation, respecti vely.