Utilizing Small Grain Cover Crops to Enhance Switchgrass Establishment in the Mid-South.

Switchgrass (Panicum virgatum L.) is anticipated to become a major crop for the emerging cellulosic biofuel industry. However, one major obstacle for large-scale production is consistent stand establishment. Use of small grain cover crops prior to planting may off-set lost production, suppress weeds, and conserve soil but possible allelopathic effects may preclude their use. Dormant-season planting may also be useful in switchgrass establishment to provide in-situ stratification. Therefore, we conducted an experiment to test these establishment strategies. The objective of this study was to determine the effects of winter small grain cover crops (wheat, rye, barley, and oats) and a fallow control on switchgrass establishment and biomass yield when seeded at three dates (March, May, and June). The study was repeated in 2009 and 2010 in a split-block (small grains as whole plots, dates as split plots) design, with three replications at three Tennessee locations. Seedling density at the end of the planting year varied but was generally greatest for March (P<0.05). For the winter annuals, results were less consistent, but oats and wheat tended to have the highest densities, fallow the lowest, and in two cases (barley and rye) divergent results based on one year and location. With respect to yields (end of second growing-season), stands planted in May tended to be greatest and those in March the lowest. Winter annuals did not affect yield in any year or location. Therefore, our research indicates that small grain cover crops are not detrimental to switchgrass establishment success or yield and may prove to be a promising management practice in the Southeast, while providing cool-season forage (or grain) during the establishment year. Overall, these strategies need to be tested over more soil types, climates, and years to verify results.