AN ECONOMIC COMPARISON OF SUBSURFACE MICROIRRIGATION WITH CENTER PIVOT SPRINKLER IRRIGATION

Simulation is used to compare water use, yields, and the relative profitabilly of fixed and towable center-pivot sprinkler irrigation and subsurface microirrigation for a corn (Zea mays L.) and soybean (Glycine max L.) rotation. Mean water use is somewhat lower on corn for microirrigation compared to sprinkler irrigation while water use differs little on soybean. Yield responses to irrigation differ little between the two systems. Relative profitability of systems depends on size. At 75 acres, subsurface microirrigation is the most profitable system while the towable center-pivot system is most profitable at 150 and 300 acres. The towable center pivot is more profitable than the fixed center pivot for all system sizes. Microirrigation is more profitable for smaller systems because of its lower per-acre investment cost and lower pumping cost. Towable center-pivot irrigation is more profitable for larger systems because its per-acre investment cost declines with increasing size.