Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2023
Publication Date: 6/27/2023
Citation: Billman, E.D., Campbell, B.T., Reay-Jones, F. 2023. Using perennial groundcover crops to suppress weeds and thrips in the Southeast Cotton Belt. Crop Science. 63(5):3037-3050. https://doi.org/10.1002/csc2.21048.
Interpretive Summary: Modern cotton production requires high inputs to obtain desirable yields that can offset the costs of production. The use of chemical herbicides and insecticides is a large component of these costs, and contributes to the development resistant weeds and insect pests over time while requiring additional machinery, fuel, and labor costs. One alternative to using chemical pesticides in cotton production is the use of perennial groundcover crops. These species are established prior to cotton planting and survive in the interrow spaces during summer and fall to suppress weed and insect pests while reducing the need for pesticide applications. A two-year study was conducted in South Carolina to evaluate the efficacy of perennial groundcovers in a cotton production system. Weedy biomass and the number of weeds per square foot were substantially reduced when perennial red and white clover species were present. Early-season insect pest pressure was also reduced when perennial clovers were present. Cotton lint yield was not negatively affected by growing perennial groundcovers species, but yields in the study were generally low. However, the perennial clover varieties used in the trial were not able to persist under heat and drought stress in the southeastern United States and eventually died out after two growing seasons. A cost-comparison indicated that producers could save up to $70 per acre if perennial groundcover crops can be maintained for multiple years and lint yields are not reduced. These findings indicate that perennial groundcover crops could aid in reducing inputs in southeastern cotton production, but current varieties require access to irrigation to persist in the region.
Technical Abstract: Modern cotton production (Gossypium hirsutum L.) in the United States relies on chemical and physical inputs that increase the environmental and monetary costs of managing the crop. Perennial groundcover crops (PGCC) may reduce inputs by persisting in the interrow spaces of the cotton crop during summer months. A two-year field study was conducted in Florence, South Carolina to evaluate growing PGCCs with cotton using a 4 × 4 Latin Square consisting of four cover crop treatments: 1) a fallow, unplanted control, 2) annual ryegrass (Lolium multiflorum Lam.) monoculture, 3) a binary red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) mixture, and 4) a trinary mixture of annual ryegrass, red clover, and white clover. Fallow and annual ryegrass treatments were killed with a burndown herbicide application, while treatments containing clovers were mowed. Plots were strip tilled and planted with cotton in May each year. Interrow biomass, weed and thrips populations, and perennial clover populations were collected from June – October along with annual lint yields from cotton harvest in October. Results indicated that interrow biomass (2,000 – 3,000 kilograms/hectare), weeds (20 weeds/square meter), and thrips (5 thrips/five plants) populations were lowest in treatments containing perennial clovers, but drought and heat stress depleted clover stands within two growing seasons. Lint yield was not affected by incorporating perennial clovers into the interrow spaces of the crop. Perennial groundcover crops may provide an effective alternative to chemical weed control in cotton, but necessitate management changes to be viable in the southeastern U.S.