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Arkansas producers planted 73,000 ha of corn and 390,000 ha of cotton in 2000, with practically all of the corn and 69% of the cotton irrigated. The University of Arkansas Cooperative Extension Service provides the Arkansas Irrigation Scheduler, a computer program to help farmers decide when to irrigate. Studies were begun at the University of Arkansas Northeast Research and Extension center at Keiser to validate the crop water use functions for corn and cotton in the Arkansas Irrigation Scheduler. Subsurface drip irrigation (SDI) was used to precisely control the water applied to plots and Watermark sensors were used to track soil moisture status. Because the corn crop had already undergone drought stress by the time the SDI system was operational, the corn portion of the study was not initiated in 2001. In the cotton study, a nonirrigated treatment was the first treatment to reach NAWF=5 (physiological cutout) and a treatment with daily applications of 100% of the estimated daily water use was the last. Days to mean maturity followed the same trend and neither factor was significantly affected by cultivar. Cultivar was significant for lint yield, but not irrigation level. Soil disturbances (precision grading, installing drip tubing and rebuilding soil beds) may have influenced responses and reduced the observed differences among irrigation treatments. The studies will continue in 2002.