Identifying optimal early-season harvest timing in annual fall forages

Authors: Billman, Eric; ALEXANDRE DE SOUZA, IGOR - Universidade Federal Dos Vales Do Jequitinhonha E Mucuri; SMITH, RICHARD - University Of New Hampshire; Soder, Kathy; WARREN, NICHOLAS - University Of New Hampshire; BRITO, ANDRE - University Of New Hampshire

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2022
Publication Date: 7/7/2022
Citation: Billman, E.D., Alexandre De Souza, I., Smith, R.G., Soder, K.J., Warren, N.D., Brito, A.F. 2022. Identifying optimal early-season harvest timing in annual fall forages. Crop, Forage & Turfgrass Management. 8(2):e20179. https://doi.org/10.1002/cft2.20179.
DOI: https://doi.org/10.1002/cft2.20179

Interpretive Summary: Fall forage production in the northern United States is complicated by the transition from warm to cold temperatures over a three-month period (September – November). Perennial cool-season forages are less productive in the fall than in spring, making annual, alternative forages useful for supplementing production. However, there is little knowledge of how annual forages respond to these temperature shifts and when tradeoffs between yield and livestock nutritional quality occur during the season. A 2-year research project conducted in New Hampshire assessed the forage mass and quality of six annual forage species (canola, forage radish, oats, spring triticale, spring wheat, and sunn hemp) not typically grown for fall harvest. Harvesting occurred 6, 8, and 10 weeks after planting, with the final harvest occurring after a killing frost. Findings from this work indicated that careful management of harvest timing in the fall in critical to maintaining a balance between forage mass and nutritive value, with most species declining in nutritive value rapidly following a killing frost. Therefore, species that rapidly accumulate high quality biomass, such as canola, oats, and triticale are most suitable for production throughout the fall grazing season.

Technical Abstract: Fall forage production in the northeastern US can be complicated by the rapid onset of cool temperatures, limiting forage availability in cool-season perennials. Annuals planted in late summer as cover crops or supplemental forage crops may have value as fall forage; however, data on their nutritive value over the short fall harvest window is lacking. This study compared six annual forage crops for their forage mass, nutritive value, and respective tradeoffs as a function of harvest time. Monocultures of canola (Brassica napus L.), forage radish (Raphanus sativus L.), oats (Avena sativa L.), spring triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum]), spring wheat (Triticum aestivum L.), and sunn hemp (Crotolaria juncea L.) were sown in August of 2015 and 2016 then harvested at three time points (six, eight, and ten weeks after planting) over the fall (September-November). A mixture of all six species was also assessed for forage mass but not nutritive value. Canola, oats, and spring wheat had the greatest forage mass, while sunn hemp had the least across all harvests. Canola and forage radish maintained the lowest neutral and acid detergent fiber (NDF and ADF) and greatest in vitro true dry matter digestibilities (IVTDMD) across all harvests, while sunn hemp and the grasses declined in IVTDMD after first and second harvest. Forage mass of the fall mix was comparable to the highest yielding monoculture at third harvest only. These results suggest that harvest time is critical to maximizing the fall forage value of late summer-sown annual crops.