Water use and yield of limited-irrigated and dryland corn.

Corn (Zea mays L.) is grown on more irrigated hectares than any crop in the Great Plains. Much of this area is irrigated from the Ogallala aquifer, which is being depleted in some areas, particularly in the central and southern portions of the region. Research was conducted at Garden City, KS, from 1994 through 1997 to evaluate the effects of various combinations of irrigation, N rate, and plant population on water use and yield of corn and to determine if limited irrigation is a viable alternative to returning irrigated hectares to dryland in an area of declining groundwater. Treatments were zero, one, two, and three irrigations, each consisting of 150 mm of water, applied to corn grown with conventional tillage (CT) and no tillage (NT). Appropriate N rates and plant populations were used with each irrigation treatment to give the management systems S0, Sl, S2, and S3. The single irrigation was at tassel (VT) and the two irrigation treatment was at VT and at the dough stage of grain fill (R4). Corn irrigated three times received a vegetative irrigation at the 9 to 10 leaf stage (V9) plus irrigations at VT and R4. Management system S1 increased yield by an average of 1.76 Mg ha -1 or 29%. On average S2 and S3 increased yields an additional 11 and 13%, respectively. No till increased yield and water-use efficiency (WUE) in 2 of 4 yr. On average NT increased yield by 0.56 Mg ha -1 , and WUE by 0.96 kg ha -1 mm -1 . Conclusions are that corn will produce adequate yields with one or more irrigations; thus, limited irrigation combined with proper fertility and plant population is a viable alternative to dryland in an area of declining groundwater.