Wheat cover crop and seed treatment for improving native warm-season grass establishment

Authors: KEYSER, PATRICK - University Of Tennessee; Ashworth, Amanda

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2021
Publication Date: 2/17/2022
Citation: Keyser, P., Ashworth, A.J. 2022. Wheat cover crop and seed treatment for improving native warm-season grass establishment. Crop, Forage & Turfgrass Management. 8(1). Article e20147. https://doi.org/10.1002/cft2.20147.
DOI: https://doi.org/10.1002/cft2.20147

Interpretive Summary: Much attention has been focused on native warm-season prairie grasses such as switchgrass, big bluestem, and eastern gamagrass because of their potential to produce large amounts of forage during drought and biomass for bioenergy, as well as their potential to serve as dual-use forage-bioenergy crops. These attributes, along with their ability to grow on marginal soils make these grasses ideal candidates for climate change adaptation and resiliency for agro-grasslands. However, despite their many advantages, they have not been widely re-adopted into production systems of the humid Southeastern US. One obstacle is consistent establishment. Establishment challenges may be the single greatest barrier for producers adopting native grasses. These problems can ultimately result in stand failures, which are expensive, result in lost production, and discourage producers from investing in improved summer forage crops, however, companion crops may improve establishment. Therefore, researchers evaluated various management practices such as seed treatment and wheat cover crops (fertilized and non-fertilized) for their ability to improve yield and plant establishment. Seed treatment improved native grass seedling density, but wheat fertilization did not affect yields. Results indicate producers could benefit from dormant season planting with seed treatment. Planting wheat cover crops could help offset lost production during the establishment year of native grasses and aid in the adoption of drought-tolerant forage options in the Southeastern US.

Technical Abstract: Switchgrass (SG; Panicum virgatum L.) and other perennial native warm-season grasses (NWSG) such as big bluestem (BB; Andropogon gerardii Vitman) and eastern gamagrass [EG; Tripsacum dactyloides (L.)] are excellent biofeedstocks and dual-purpose biomass-forage crop candidates. However, reliable establishment continues to be a challenge. Therefore, we conducted an experiment at two locations in Tennessee, repeated over two years (2012 and 2013) to evaluate improved establishment strategies for BB, EG, and SG. Treatments included a wheat (Triticum aestivum L.) cover crop with and without inorganic-nitrogen (N) (67 and 0 kg ha-1) and seed treatment (Gaucho XT and an untreated control). Although establishment success varied by site and year, SG generally produced stands with greater seedling densities than BB, with EG producing the weakest stands. The N fertilization treatment did not affect NWSG seedling density or yields in subsequent years at either location for either planting year. Seed treatment improved seedling density in 2013 at one location for SG but not the other two species (P = 0.029). At the second location, seed treatment improved seedling density (4.6 vs. 3.1 seedlings m-2) across all species (P = 0.006), apparently driven by response of BB (7.4 vs. 4.7 seedlings m-2; P = 0.094). Neither species nor treatment influenced (P <0.001) yield, which increased each year (4.29, 6.02, and 8.06 Mg ha-1) across all species. Based on these results, dormant-season planting in wheat can produce acceptable stands of NWSG while offsetting establishment year production losses and seed treatments offer some promise for improved success.