OPTIMUM LATERAL SPACING FOR SUBSURFACE DRIP-IRRIGATED CORN

Abstract

A two-year study was initiated in the spring of 1990 on a Keith silt loam soil (Aridic Argiustoll) in northwestKansas to determine the optimum dripline lateral spacing for irrigated corn (Zea mays L.) using subsurface driplinesinstalled at a depth of 40-45 cm in a direction parallel to the corn rows. Average corn yields were 13.6, 12.8, and12.2 Mg/ha for dripline spacings of 1.5, 2.3, and 3.0 m, respectively, for a seasonal-irrigation amount of 462 mm. Yieldsdecreased to 10.8 and 9.3 Mg/ha when irrigation was reduced by 33 and 50% for the wider 2.3- and 3.0-m driplinespacings, respectively. The wider dripline spacings resulted in nonuniform horizontal distribution of available soil water.As a result, yields decreased with horizontal distance from the dripline. The highest yield, highest water use efficiency,and lowest year-to-year variation were obtained with the 1.5 m dripline spacing. An economic analysis indicated thatbecause yield reductions were so great, the wider dripline spacings would be justified only at very high dripline costs andor very low corn grain prices.