Wheat yields in Kansas might have increased during the 2015 harvest, but test weights and protein content were down statewide. According to the United States Department of Agriculture National Agricultural Statistics Service, data was collected from 7,233 carlot samples from 47 counties which showed an average test weight of 59.9 pounds per bushel. In comparison, the 2013 and 2014 harvest averages were 60.7 and 60.5 pounds per bushel, respectively.
Closer to home, Barton County farmers fared better, Barton County Extension Agent Alicia Boor said. “Everybody was relatively pleased.”
Yields were above average and test weights were really good, she said. She had reports of test weights in the 70s.
Protein content and yield have an inverse relationship. When yields go up, protein content generally falls, and that rule of thumb held true in 2015. While the current year’s harvest was increased about 35 percent from last year, protein content for the state decreased from 13.4 percent to 12.7 percent. While it is lower than last year, 12.7 percent is actually still above the 10-year average of 12.4 percent. The Southwest and North Central Districts tied for the highest protein content at 13.1 percent.
While this year’s last minute rains increased the size of the Kansas crop by millions of bushels, they also played heavily into the decreased test weights statewide. While rain during the wheat’s growing season helps the plant grow, rains at harvest time can decrease test weights seemingly overnight by 2-3 points. As wheat is harvested, the dry, smooth kernels can be packed tightly together into a bushel. When moisture is introduced to a kernel after the first dry-down, the kernel will swell, much like a puffed wheat cereal.
In Barton County, “we really just got the rain at the right time,” Boor said.
Even when the kernel dries, it can’t shrink down to its original volume. Instead, it maintains the same weight, but the kernel takes up more space. So harvest time rains don’t mean less grain to haul in, it reduces the number of kernels per bushel which results in a test weight decrease. According to the Kansas Weather Data Library, Kansas received 188 percent more moisture than normal in May, averaging 7.73 inches statewide.
Mary Knapp, climatologist with Kansas State University, attributed the rains in part to moisture opening up from the Gulf of Mexico mixing with cold fronts moving across the state that “opened a fire hose pointed north.” While these rains helped bump yields, it also created the right climatic conditions for thunderstorms to build and stay over small geographic areas. The remnants of these storms caused issues like lower test weights and disease.
The 2015 crop’s moisture content averaged 11.2 percent, down 11.9 percent, but equal to the 10-year statewide average. With the test weight and protein content lowered, wheat’s graded quality also decreased. Samples graded No. 1 accounted for 53 percent, down from 73 percent last year. No. 2 samples accounted for 38 percent, compared to 26 percent in 2014, while 9 percent graded No. 3 or below.
Test weight, protein content, grade and defect determinations are made by Kansas Grain Inspection Service Inc. The data are summarized by the USDA’s National Agricultural Statistics Service.