Evaluation of Alternative Cover Crops for Cotton on the Southern High Plains of Texas

Abstract

Cotton (Gossypium hirsutum L.) is typically grown as a monoculture on the Southern High Plains of Texas, which results in reduced soil organic matter and increased soil erosion. Wheat historically has been used as a cover crop in this region, but other species may protect the soil while using less soil moisture. During 1991 and 1993, establishment, biomass production, moisture utilization and nutrient accumulation were measured on four cultivars of Brassica spp., one cultivar of Crambe (Crambe abyssinica Hochst. Ex. R. E. Fries), three cultivars of Pisum spp. and winter wheat (Triticum aestivum L). These evaluations were conducted on either a Pullman clay loam (fine, mixed, thermic Torreretic Paleustolls) or on an Amarillo fine sandy loam (fine-loamy, mixed, thermic Aridic Paleustalfs) near Lubbock, TX. Increased use of cover crops across this region could significantly reduce wind erosion. Late August or early September planting was essential for establishment and survival of Brassica species. With early seeding and optimum moisture conditions, interseeded cover crops produced biomass yields in excess of 1 Mg ha^-1. The larger-seeded legumes and winter cereals successfully established even when emergence was delayed until late fall, but delayed establishment (October to January) failed to provide total biomass production greater than 1 Mg ha^-1. Winter wheat planted in early February produced only 0.6 Mg ha^-1 of total biomass even when fertilized with up to 33 kg ha^-1 of nitrogen (N) while peas produced only 0.1 Mg ha^-1 of biomass. These studies indicate that cover crops should be established in September to provide optimum soil protection. Neither spring- nor fall-planted cover crops significantly increased yield of the subsequent cotton crop. Soil moisture utilized by cover crops usually was not significantly higher than losses measured in the noncultivated control.