Evaluating the agronomic impact of warm-season annual grasses interseeded into orchardgrass

Authors: Burt, Justin; Soder, Kathy; Jaramillo, David

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: Forage production in cool-season perennial pastures commonly found in temperate regions of the US, such as the Northeast, is greatly reduced during summer due to lack of moisture and high temperatures. There is interest in incorporating warm-season annual (WSA) grasses, which grow well during hot weather, into these perennial pasture to increase overall forage production, decrease land requirements, and reduce feed costs on grazing dairy and livestock farms. Results of this study found that including WSA grasses (sorghum-sudangrass, pearl millet, or teff grass) into an established orchardgrass pasture did not negativly impact the total amount of forage produced or the nutritional value for grazing livestock compared to orchardgrass monocultures. All WSA evaluated competed with the orchardgrass for resources, such as water and fertility, which may hurt long-term longevity of the pasture. Future research is needed to evaluate other warm-season annual forages in perennial pastures to improve forage and animal productivity of pasture-based dairy and livestock systems.

Technical Abstract: Pasture systems in the northeastern US are primarily comprised of cool-season perennial grasses. However, these systems are subject to a lag in forage production during the hot summer months. Incorporating warm-season annual grasses (WSA) into these forage systems may improve overall forage productivity, especially for producers with a limited land base. Therefore, the objective of this study was to compare the agronomic impact of WSA interseeded into orchardgrass (Dactylus glomerata L.; OG) and harvested at two different intervals. This study compared monocultures of OG to OG interseeded with sorghum-sudangrass (Sorghum bicolor × S. bicolor var. sudanense; SSG), pearl millet (Pennisetum glaucum L.; PM) or teff grass (Eragrostis tef L.; TEFF), harvested on either a 6-week or 12-week interval. Results indicated that inclusion of WSA into OG did not improve total herbage accumulation or nutritive value beyond the OG monoculture at either harvest interval (p > 0.42). However, inclusion of WSA into OG did impact the proportion of OG in the stand at both harvest intervals (p < 0.01). The greatest impact was observed in plots interseeded with SSG, in which there was a ~14% and ~25% decrease in OG compared to OG monoculture plots when harvested on a 6-week and 12-week interval, respectively. This study concluded that interseeding WSA into OG did not improve agronomic parameters of the stand compared to OG despite implementing different harvest frequencies. Future research is warranted evaluating the impact of warm-season annual legumes under similar conditions on the forage production of cool-season perennial grass pastures.