Kansas State University scientists may be giving wheat growers reason to watch the weather more than they did before in October – and, for that matter, in May and June.

The scientists’ sweeping look at 55 years’ worth of historical wheat yield data showed that for every 1-inch increase in October precipitation, dryland wheat yield increased 4 to 5 bushels per acre. For every 1-degree (F) increase in fall (October or November) temperature, dryland and irrigated wheat yields both decreased about 1 bushel per acre.

In May, for every 1-degree increase in temperature, irrigated wheat yields increased 1 bushel per acre. In June, however, for every 1-degree increase in temperature, dryland and irrigated wheat yields both dropped about 1 bushel per acre.

“Our goal with this study was to determine the change in western Kansas wheat yields for the past 55 years, as influenced by precipitation and temperature,” said John Holman, Garden City-based K-State Research and Extension agronomist. He collaborated on the study with three other K-State agronomists: Tribune-based Alan Schlegel and Manhattan-based Curt Thompson and Jane Lingenfelser.

In the study, “Influence of Precipitation, Temperature, and 55 Years on Winter Wheat Yields in Western Kansas,” the researchers compiled data from four K-State Research and Extension experiment stations in western Kansas (Colby, Garden City, Hays and Tribune). They included dryland and irrigated wheat.

“Winter wheat is the most common crop in Kansas with 8.6 million acres grown in 2010,” Holman said. “However, the number of acres planted to wheat has steadily decreased since 1993, when 12.1 million acres of wheat were planted in the state.”

Several studies have evaluated wheat yield changes over time, he added, noting that wheat yields in the overall Great Plains have increased by close to 1 percent each year since 1959. About 50 percent of the increase is likely due to genetic improvements, but limited information has been available about the impacts of environment on crop yield over time. 

K-State’s research is the first evaluation of the effects of monthly temperature and precipitation for dryland and irrigated wheat.