Corn Yields and Profitability for Low-Capacity Irrigation Systems

ABSTRACT. In many areas of the central U.S. Great Plains irrigation well capacities are decreasing due to declines in the Ogallala aquifer. Many producers using furrow surface irrigation are faced with a decision on whether they should convert to a higher efficiency center pivot sprinkler irrigation system. An irrigation scheduling model using 27 years of climatic data for western Kansas was combined with a corn yield production function and economic model to simulate crop yields and economics under four combinations of irrigation system and application efficiency for six different irrigation capacities. Center pivot sprinkler irrigation systems were found to give higher corn yields and greater profitability than furrow surface irrigation, particularly when system flow rates were less than 40 L/s. Sprinkler irrigation systems with application efficiencies of 100, 95, and 85 % and a furrow surface irrigation system with 70 % application efficiency produced simulated crop yields of 12.3, 12.2, 12.1, and 11.3 Mg/ha, respectively, when irrigation capacity was 6.35 mm/day. Reducing the irrigation capacity to 2.54 mm/day reduced yields to 9.4, 9.2, 8.9, and 8.3 Mg/ha for the respective irrigation systems. Net annual returns for a 65 ha field were increased by US$1000 to $4000 with center pivot sprinkler irrigation compared to furrow surface irrigation for system flow rates between approximately 20 and 40 L/s. Labor savings with sprinkler irrigation are a significant factor in profitability, but increased crop yields are also very important, particularly at lower system flow rates of approximately 20–30 L/s