LEPA corn irrigation with limited water supplies

Declining water tables on the Southern High Plains may reduce irrigated corn area in the region and/or cause a shift to deficit irrigated production. This research was conducted to determine optimum water management practices for low energy precision application (LEPA) irrigation of corn with limited water supplies and to evaluate the prospects for deficit irrigation based on yield response. Irrigation quantities ranged from deficit to excess irrigation [0.4, 0.7, 1.0, and 1.3 BI (BI = ET- rainfall)] and were applied both alternate and every furrow at intervals of 3, 6, 9, and 12 days from 1989 through 1991. The study was conducted at Halfway, Texas, on a moderately permeable (2.5 mm h-1) Olton loam soil. Seasonal irrigations (1.0 BI) ranged from 299 mm in 1991 to 453 mm in 1990. Highest corn grain yields were obtained with three-day and six-day irrigation intervals (11.1 Mg ha-1 each). Significant yield declines occurred for the 9-day (10.6 Mg ha-1) and 12-day (10.2 Mg ha-1) intervals. Grain yield increased with water quantity and ranged from 8.3 Mg ha-1 for the 0.4 BI treatment (147 mm average seasonal irrigation) to 12.4 Mg ha-1 for the 1.3 BI treatment (428 mm average irrigation). Applicator location (alternate vs. every furrow) had no effect on yield except for the 0.7 BI quantity treatment where alternate was greater than every furrow (P less than or equal to 0.05). Water use efficiency responded significantly to water quantity (P less than or equal to 0.05) with the highest occurring also at 0.7 BI (1.90 kg m-3). This research showed that irrigation quantities applied at infrequent intervals typical of furrow irrigation (9 to 12 days) can be reduced as much as 30% by lowering the irrigation interval to six days or less without corn grain yield reduction. It was concluded that substantial water savings can be achieved by adopting a high frequency LEPA irrigation schedule and a moderate deficit irrigation management program (0.7 to 0.8 BI) without experiencing significant yield decline, but rather, resulting potentially in increased net returns.