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When several wheat varieties are planted in a field, one variety may be susceptible to a particular airborne fungal disease (shown as yellow, infected by fungal spores), while another may be resistant to the disease (shown as green, thriving). Fields are unpredictable environments, so combining varieties that have complementary strengths can help stabilize yields.

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Planting Wheat Blends Means Higher Yields

By Rosalie Marion Bliss
May 8, 2007

A two-year comparative study of wheat plantings has shown that blends of complementary wheat varieties out-yielded single varieties, or nonblends, by an average of 2.3 bushels per acre. The blends—mixtures of two or three varieties with carefully matched traits—showed a 3.2-percent yield advantage over the single, or "pure," variety stands.

The study was conducted by plant pathologist Christina Cowger with the Agricultural Research Service (ARS), the U.S. Department of Agriculture's chief scientific research agency. Cowger works in the ARS Plant Sciences Research Unit, Raleigh, N.C.

Environmental stresses such as disease and drought occur unpredictably year in and year out. And wheat varieties have their own inherent weaknesses that cause fluctuations in yield under suboptimal conditions. For example, a variety may be resistant to some diseases, but susceptible to others. Or a variety may yield well in the absence of disease, but fall short of its yield potential when an epidemic occurs.

From eight pure varieties, Cowger developed 13 blends, matching complementary features for best advantage. Each blend was made with equal numbers of seeds of each variety used. She planted the 13 wheat mixtures, and eight pure stands, in three different North Carolina counties representative of the state's sandy, organic and clay soil environments. All 21 entries were planted in a two-year, replicated experiment in each of the three representative locations.

Cowger studied the blends' response to powdery mildew, leaf rust, soilborne viruses and other diseases. She also evaluated yield, test weight, and quality factors at all three test sites. For the analysis, Cowger averaged the data over the 2-year period of 2005 and 2006.

Read more about the research in the May/June 2007 issue of Agricultural Research magazine.