Evaluating the effects of cotton intercropping on cool-season perennial forage persistence, forage mass, and nutritive values in the southeastern United States

Authors: Billman, Eric; Myers, William - Tillman

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2024
Publication Date: 6/27/2024
Citation: Billman, E.D., Myers Jr, W.T. 2024. Evaluating the effects of cotton intercropping on cool-season perennial forage persistence, forage mass, and nutritive values in the southeastern United States. Agronomy Journal. https://doi.org/10.1002/agj2.21625.
DOI: https://doi.org/10.1002/agj2.21625

Interpretive Summary: Integrated cropping systems that combine forages and row crops are becoming increasingly commonplace among livestock and row crop producers for their economic and ecosystem service benefits. These systems typically rely on producing annual forages during winter and spring and row crops during summer and fall. However, there has been little examination of how to successfully combine cool-season perennial forages with row crops unique to southeastern U.S. farmers. Cotton is widely grown in the Southeast but has few workable annual forages to rotate with due to its late-fall harvest time. Perennial forages that persist year-round between the rows of cotton could maximize forage and cotton productivity while reducing weed pressure during spring. A two-year study was conducted in the South Carolina cotton belt to assess the viability of growing cool-season perennial forages, perennial white and clover, in tandem with a cotton crop. When mixed, perennial white clover persisted better than perennial red clover. However, heat and drought stress during the second year resulted in stand losses for red and white clover species. A three-species mixture of annual ryegrass, red clover, and white clover was most effective at suppressing winter annual weeds from February to April, reducing the need to spray chemical herbicides before planting cotton. During the second year of perennial growth, the red and white clover mixture suppressed weeds at similar levels to an annual forage grass. Perennial clovers also improved the nutritional content in a mix of grass and clovers. These findings showed that cool-season perennial species can improve the forage part of integrated cropping systems for the southeastern U.S., provided that either irrigation is accessible or varieties tolerant to heat and drought stress are developed.

Technical Abstract: Integrated crop-livestock systems provide important agronomic and economic benefits to producers. However, little attention has been given to integrating forages into row crop systems unique to the southeastern U.S. This study assessed the viability of intercropping perennial, cool-season legumes with cotton (Gossypium hirsutum L.) during the summer months in the Southeast Coastal Plain over two production years. Treatments included a weedy fallow, annual ryegrass (Lolium multiflorum Lam.) monoculture, a red (Trifolium pratense L.) and white clover (Trifolium repens L.) mixture, and a three-species mixture of annual ryegrass, red clover, and white clover. Plots were established in fall 2020 with forage grown until May 2021 and 2022, when plots were strip-tilled and planted with cotton. Cotton was managed with minimal herbicide use to preserve perennial clovers. Results indicated white clover persisted longer than red clover (> 40 plants m-2 vs. < 40 plants m-2), and the presence of perennial clovers suppressed weeds at similar levels to the annual ryegrass monoculture (35 weeds m-2) during the second spring. Perennial clovers grew taller (4 – 5-cm) when mixed with annual ryegrass. The presence of clovers mixed with annual ryegrass during the second spring reduced acid detergent fiber (ADF) concentration and increased crude protein (CP) concentration (280 g ADF kg-1; 167 g CP kg-1) compared to the annual ryegrass monoculture (315 g ADF kg-1; 126 g CP kg-1). Benefits of intercropping perennial forages with cotton were maximized during the second year of growth, but future work is necessary to improve stand survival.