Using Perennial Groundcover Crops to Suppress Weeds and Thrips in the Southeast Cotton Belt

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 2-year field study was conducted in Florence, SC, to evaluate growing PGCCs with cotton using a 4 x 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 to October along with annual lint yields from cotton harvest in October. Results indicated that interrow biomass (2000-3000 kg ha(-1)), weeds (20 weeds m(-2)), and thrips (five thrips per five plants(-1)) populations were lowest in treatments containing perennial clovers, but drought and heat stress reduced 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 United States.