8 Years of Growing Cover Crops in the Semi-Arid Great Plains.

Producers are interested in growing cover crops in place of fallow. Growing a cover crop during the fallow period would increase system profit if the benefits of growing the cover crop exceed the expense of growing the crop plus the potential negative yield impacts on the following crop. Benefits of growing a cover crop were shown in high precipitation regions, but limited information is available on growing cover crops in the semiarid Great Plains. A study from 2007–2015 evaluated cover crops, annual forages, and short season grain crops grown in place of fallow. In the first experiment (2007-2012) the crop rotation was no-till wheat-fallow, and in the second experiment (2012-2015) the rotation was no-till wheat-grain sorghum-fallow. This report presents results from both experiments. Wheat yield was affected by growing a crop in place of fallow, but there was no difference in wheat yield whether the crop was grown for forage or cover. Wheat yield following crops grown in place of fallow was dependent on the amount of precipitation received during the fallow period and the winter wheat growing season. In dry years (2011-2014), growing a crop in place of fallow reduced wheat yields up to 75%, yet growing a crop in place of fallow had little impact on wheat yield in wet years (2008-2010). The length of the fallow period between cover crop termination and wheat planting also affected wheat yields. Fallow periods less than 120 days between cover crop termination and wheat planting tended to reduce wheat yield greater. Cover crops did not improve wheat or grain sorghum yields compared to fallow. Cover crops always resulted in less profit than fallow, while annual forages and grain peas increased profit compared to fallow in wet years. In dry years fallow was the most profitable. The negative effects of annual forages on wheat yields and profit might be minimized by using flex-fallow. Flex-fallow is the concept of only growing a crop in place of fallow in years when soil moisture at the time of annual forage planting and precipitation outlook for the coming year are favorable. This determination is made at the time of making the decision of whether or not to plant a forage crop within the traditional fallow period. In years that soil moisture and precipitation outlook are not favorable, then a forage crop is not planted and fallow should be practiced.