The impact of field size and energy cost on the profitability of supplemental corn irrigation

Supplemental irrigation in corn production is increasing for humid regions across the world. Little is known about the profitability of irrigating corn in the humid southeastern region of the United States. Our objective was to determine the breakeven price of corn where investment in center-pivot irrigation would be profitable in Tennessee. We considered the effects of field size, energy price, and energy source on the breakeven price of corn. We estimated yield response to nitrogen (N) for irrigated and non-irrigated corn, and allowed expected yield and economically optimal N fertilization to vary with the breakeven price. Field size and the cost of running electricity to the center-pivot were two important factors in choosing between diesel and electricity as the energy source. The breakeven price of corn ranged between $249-$283 Mg−1 for the small-sized field, $168-$190 Mg−1 for the medium-sized field, and $149-$171 Mg−1 for the large-sized field. As field size increased, electricity became more economically viable relative to diesel. At current corn prices, irrigating corn appears profitable on fields greater than 51 ha. However, historically, the probability for the breakeven corn price occurring is zero for the small-sized field, between 6-14% for the medium-sized field, and 12-27% for the large-sized field.