Establishment strategies for native warm-season grasses: Organic and conventional approaches

Native warm-season grasses (NWSG) adoption is limited partly due to establishment challenges, especially weed competition. The objective was to develop establishment protocols for switchgrass [Panicum virgatum (L.) ‘Vitman’; SG], eastern gamagrass [Tripsacum dactyloides (L.); EG] and a mix of Indiangrass [Sorghastrum nutans (L.) ‘Nash’; IG] and big bluestem (Andropogon gerardii ‘Vitman’; BB) under organic and conventional herbicide management across three sites in Ohio from 2021 to 2024. Three strategies were evaluated: (a) Conventional, no-till with herbicide; (b) Conventional + cereal rye cover crop (CC); and (c) Organic, with tillage and summer (sorghum –sudangrass [Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud.) de Wet & Harlan} + cowpea [Vigna Savi]) and fall (oats [Avena L.]) cover crops. Organic treatments used no herbicide and Conventional treatments used glyphosate (SG, EG) or imazapic (IG/BB), with some sites receiving 2,4-D (2,4-Dichlorophenoxyacetic acid). Results demonstrate that in Conventional treatments, with and without cover crops, NWSG growth suppressed weeds and forage mass was stabilized by Years 2 and 3. The Organic system consistently had the lowest forage and the greatest weed mass. For most locations/years, the greater NWSG mass and cover and lowest weed mass and cover occurred in the IG/BG mix compared with SG and EG, probably due to the selective herbicide use reducing weed pressure and promoting faster forage growth. Forage nutritive value was greater in the IG/BG mix. However, all NWSG species had moderate to good nutritive value, according to USDA hay standards, which do not specify animal category. In conclusion, successful NWSG establishment required chemical weed control, and adding cover crops with herbicide was less effective than herbicide alone.