U.S. Department of Agriculture (USDA) scientists in Tifton, Ga., are providing guidance to growers by showing that strip tillage and cover crops are important practices for reducing erosion from sandy soils in the Southeastern United States and for enhancing soil quality.
Dinku Endale, an agricultural engineer with the USDA, Agricultural Research Service (ARS), and his ARS colleagues David Bosch, Thomas Potter and Timothy Strickland compared surface runoff and sediment losses from two common tillage systems between 2000 and 2009, including years with severe drought and heavy rainfall. They collected runoff from fields rotated between peanut and cotton crops that were either conventionally tilled or strip-tilled.
Conventional tillage mixes all crop residues into the soil prior to planting while strip tillage does so only in narrow four-to-six-inch-wide strips where the seeds are planted. The remaining area is left undisturbed so that cover crop residues remain on the surface, providing protection from water and wind erosion. The researchers also used rye as a winter cover crop to protect the soil, increase organic matter and hold nutrients remaining from previous cropping seasons that otherwise might leach away.
The results provide a clear picture of the advantages of strip tillage. About 20 percent of the rain on conventionally tilled fields was lost in surface runoff compared with only 12 percent from the strip-tilled fields. The runoff from strip-tilled fields carried 87 percent less sediment than that from the conventionally tilled fields. Sediment losses exceeded the acceptable threshold for the soil in 3 of the 10 years on the conventionally tilled fields, but they never exceeded the threshold on the strip-tilled fields.
The ARS researchers also found that, with respect to reducing erosion and surface runoff, the benefits of strip tillage were enhanced with cover crops.
The study comes at a critical time. The increased prevalence of herbicide-resistant weeds has prompted some farmers to revert from strip tillage to conventional tillage as a weed control strategy. Climate change also is expected to bring more intense rainstorms that increase runoff and soil erosion from farm fields.