FOOD SECURITYMore U.S. Crops to Require Irrigation

With climate change, irrigating more crops in the United States will be critical to sustaining future yields, as drought conditions are likely to increase due to warmer temperatures and shifting precipitation patterns. Yet less than 20% of the nation’s croplands are equipped for irrigation.

A Dartmouth-led study finds that by the middle of the 21st century, under a moderate greenhouse gas emissions scenario, the benefits of expanded irrigation will outweigh the costs of installation and operation over an expanded portion of current U.S. croplands.

The results show that by midcentury corn and soybeans that are currently rainfed would benefit from irrigation in most of North Dakota, eastern South Dakota, western Minnesota, Wisconsin, and Michigan. Soybean farmland that relies on rain throughout parts of Indiana, Illinois, Ohio, Kentucky, Kansas, and Oklahoma would also benefit from irrigation. The findings are published in Communications Earth & Environment, an open-access journal from Nature Portfolio.

Installing, maintaining, and running irrigation equipment comes at a significant cost to farmers, as much as $160 per acre per year. “Our work essentially creates a U.S. map of where it will make the most sense to install and use irrigation equipment for corn and soybean crops in the future,” says first author Trevor Partridge, Guarini ’21, a Mendenhall Postdoctoral Fellow and research hydrologist with the U.S. Geological Survey Water Resources Mission Area who conducted the study while working on his PhD at Dartmouth.

The High Plains region, including Nebraska, Kansas, and northern Texas, has historically been one of the most heavily irrigated areas, and was found to have the highest current economic returns for irrigation. However, the increasing costs of drought are pushing farmers to invest in irrigation throughout regions of the Corn Belt and southeastern U.S., and the long-term economic return on these investments is difficult to predict.

To conduct the cost-benefit analysis of irrigating corn and soybeans, the researchers ran a series of crop model simulations. They applied several global climate projections that span the range of potential future climates—hot and dry, hot and wet, cool and dry, cool and wet, each relative to the average climate projection—to simulate future crop growth under fully irrigated or rainfed conditions.