Water-Table Depth and Irrigation Effects on Applied-Water-Use Efficiencies of Three Crops

ABSTRACT INFORMATION is needed on crop response to com-binations of water-table depths and irrigation treat-ment to properly design irrigation and drainage systems. A 3-yr field experiment was conducted on a Hecla sandy loam soil with three water-table depths (treatments)— shallow, medium, and deep—and with four weekly sprinkler irrigation application amounts from 0 (precipi-tation only) to 1.5 times calculated irrigation require-ment. Production of corn (grain and total dry matter), sugarbeets (sucrose), and alfalfa, and applied-water-use efficiencies (AWUE) were highest from the shallow water-table treatment without irrigation. Plant yield responses from deeper water tables increased with ir-rigation amounts but never equalled those for the shal-low water table without irrigation. The probable reason for highest AWUE in the shallow water-table treat-ment is that crop roots obtained water from the slowly receding water table during the growing season. Deep percolation losses seemed to increase with irrigation amounts and were greatest for the shallow water table. These results challenge the agricultural industry to de-sign drainage and irrigation systems to fit the needs of the crop.