|RICHWINE, JONATHAN - University Of Tennessee|
|KEYSER, PATRICK - University Of Tennessee|
|HANCOCK, DENNIS - University Of Georgia|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2021
Publication Date: 6/28/2021
Citation: Richwine, J., Keyser, P., Hancock, D., Ashworth, A.J. 2021. Using a browntop millet companion crop to aid native grass establishment. Agronomy Journal. 113:3210-3221. https://doi.org/10.1002/agj2.20739.
Interpretive Summary: In recent years, considerable attention has been focused on native warm-season grasses such as big bluestem and switchgrass because of their potential high forage production during drought, biomass for bioenergy, and for integrated forage-biomass production. These attributes 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 (two canopy management strategies and three nurse crop seeding rates) for their ability to improve yield and plant establishment. Results indicate producers could benefit from improved establishment by using the lower seeding rates of companion crops. This would 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: Consistent native warm-season grass (NWSG) establishment strategies are needed for wide-scale production. To address this, two establishment experiments were conducted at the East Tennessee AgResearch and Education Center in Knoxville, TN, 2016-2017 and repeated 2017-2018, to evaluate big bluestem (BB; Andropogon gerardii Vitman) and switchgrass (SG; Panicum virgatum L.) establishment with browntop millet [BTM; Urochloa ramosa (L.) Nguyen] as a companion crop. Each experiment was a randomized complete block arranged as a 2x3 factorial. Treatments included two canopy management strategies [MNGT; harvests based on BTM maturity for hay (HAY) or clipping to control BTM competition with NWSG seedlings (CLIP)] and three BTM seeding rates [RATE; 0 (control), 11.2 (half recommended rate), and 22.4 (full recommended rate) kg pure live seed (PLS) ha-1]. Only RATE affected BB and SG density at dormancy. In all cases, the control had greater NWSG density than the full rate, indicating a BTM companion crop would impede rather than improve BB and SG establishment. All BTM seeding rates resulted in acceptable stands (=5.4 plants m-2) of BB in 2016 and BB and SG in 2017, whereas only the control allowed for acceptable stands of SG (8.5 plants m-2) in 2016. Browntop millet HAY treatments produced a mean cumulative dry matter (DM) yield of 3.15 and 2.68 Mg ha-1 in 2016 and 2017, respectively. Therefore, while BTM did not improve NWSG establishment, it may help offset lost production during the NWSG establishment year.