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Why are test weights in wheat so low this season?
Kansas Test weights of wheat have been unusually low in much of Kansas this year, especially in areas east of Dodge City, said Jim Shroyer, K-State Research and Extension crop production specialist. That affects everything from seed quality to grain quality. The basic reason is that leaves were diseased or killed at a critical stage of wheat development this year, said Erick DeWolf, K-State Research and Extension plant pathologist. It's not unusual for leaves of wheat in Kansas to die before the kernels have filled, but this year the leaves died earlier than normal in many cases--as early as the flowering stage in the most extreme cases. By the calendar, leaf rust did not come into Kansas much earlier than normal and there wasn't any early heat or drought stress, so why did the leaves die at such an early stage of growth? "The reason is that wheat development was slow this spring, due to freeze injury and cool weather. When leaf rust came in, the wheat was in an earlier stage of development than normal," DeWolf explained. "In addition, other leaf diseases such as powdery mildew, tan spot, and speckled leaf blotch continued to be active later into the spring than normal because of the cool, wet conditions. Along with leaf rust, these diseases eventually helped kill the leaves at an early stage of wheat development in some cases." "The early April freeze either killed or damaged the main tillers. If the main tillers were killed, secondary tillers began growing. Even if the main tillers were only damaged, they resumed growing slowly. Where the freeze damaged the stems, the wheat suffered from limited flow of water and nutrients to the developing grain. The end result was that the wheat developed more slowly than normal after the first of April, and was at a critical stage of kernel development when the leaves were lost," the agronomist explained. Waterlogged conditions also contributed to low test weights, Shroyer said. Where wheat is waterlogged, the roots are starved of oxygen and cannot supply the grain with water and nutrients. Wet soil conditions can also lead to crown rot, which reduces the flow of water and nutrients to the grain. Other causes of low test weight include the presence of cheat, rye, and other grassy weeds; an unsuccessful attempt of the plants to completely fill a third or fourth berry; rainy weather at harvest time; and inherent variety differences, Shroyer said. A 4 8/6/07 Date: 7/23/07
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