Increased drought portends lower future crop yields in US midwest

Newswise via North Carolina State University: Increasingly harsh drought conditions in the U.S. Midwest’s Corn Belt may take a serious toll on corn and soybean yields over the next half-century, according to research published today in the journal Science. Corn yields could drop by 15 to 30 percent, according to the paper’s estimates; soybean yield losses would be less severe.

North Carolina State University’s Roderick Rejesus, associate professor of agricultural and resource economics and a co-author of the Science paper, says that corn and soybean yields show increasing sensitivity to drought, with yields struggling in dry conditions in Iowa, Illinois and Indiana during the 1995 to 2012 study period.

“Yield increases are getting smaller in bad conditions,” Rejesus said. “Agronomic and genetic crop improvements over the years help a lot when growing conditions are good, but have little effect when growing conditions are poor, like during droughts.” U.S. corn and soybeans account for approximately 40 and 35 percent of global production, respectively, making the results important to the world’s food supply.

Using field data over an 18-year period, the researchers point to the effects of vapor pressure deficit (VPD) on corn and soybean yields. VPD includes
temperature and humidity measures; extremes at either end of this variable signify drought or too much water for crops. Akin to the sweet spot on a baseball bat, the best VPD condition is a value in its middle range.

Some 29 climate estimates modeled in the paper suggest that VPD will rise significantly over the next 40 years, bringing on more severe drought conditions. The researchers ran the same tests using the Palmer Drought Severity Index, another widely used measure capturing nationwide temperature and humidity, and reported similar results. They also ran the same tests for a broader group of Corn Belt states to include South Dakota, Nebraska and Kansas. Those tests confirmed the results found in Iowa, Illinois and Indiana....

NASA image of crops growing in Kansas. Healthy, growing crops are green. Corn would be growing into leafy stalks by late June (when this photo was taken). Sorghum, which resembles corn, grows more slowly and would be much smaller and therefore, possibly paler.