An Analysis of Irrigation Scheduling Methods for Corn

ABSTRACT IRRIGATION schedules for corn grown in Washington's Columbia Basin during 1984 and 1985 in silt loam and sandy loam soils recommended by three commercial irrigation schedulers were analyzed using the SPAW-IRIG model. Alternate irrigation strategies were simulated with SPAW-IRIG and compared to those recommended by the commercial schedulers. Simulated irrigation depths and yields compared well the schedulers results for silt loam fields, but much more water was applied to sandy loam fields than simulations indicated was necessary for full irrigation. As compared to irrigating every three days, deficit irrigations scheduled by a yield reduction index (YRI) showed a potential savings of at least 280 mm of applied water and more than $90/ha increase in net economic returns.