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Cotton seedlings emerge from strip-tilled field.
Strip tillage helps in both wet and dry years. Above, cotton seedlings emerge from a strip-tilled field. Image courtesy Dan Mott, North Carolina State University.

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Conservation Tillage: Good for Drought and Wet Years

By Sharon Durham
December 5, 2007

Conservation tillage studies by Agricultural Research Service (ARS) scientists in Georgia indicate that this farming practice carries benefits beyond drought years, by also reducing runoff and erosion in wet years.

This conservation tillage research began in 1998. Since then, farmers in Georgia have experienced both drought years and wet years—the first four being drought years. Then, in 2002, conditions moderated, and Georgia received above-average rainfall in 2003 and 2005. Rainfall was below normal in 2004, 2006 and 2007.

Led by hydraulic engineer David Bosch, environmental chemist Thomas Potter, and soil scientist Clint Truman at the ARS Southeast Watershed Research Laboratory in Tifton, Ga., the research indicates that strip-till—a form of conservation tillage—reduces runoff, increases infiltration and increases water available for crop production.

The greatest benefit of strip-till occurs during dry years. Strip-till systems enhance infiltration of rainfall and allow more water to get to plant roots. Any additional water reaching the plant roots during a dry year benefits the grower through increased yields and reduced irrigation. Conventional tillage systems lose more water to surface runoff because there is no protection on the soil surface, and the soil absorbs the full impact of raindrops, leading to sealing and compaction of the soil.

In wet years, depending on when rainfall occurs, both conventional and conservation tillage systems can have adequate plant-available water for crop growth. However, strip-till systems continue to provide increased infiltration and reduced runoff, lessening the potential for surface-runoff-related environmental problems.

In the fall and winter, when evaporation and transpiration are low, infiltrating water often exceeds the soil's capacity to retain it. When considering all water losses, conventional-till systems lose more water because of the greater surface runoff.

During wet or dry growing seasons, strip-till benefits Georgia growers by increasing the amount of rainfall or irrigation water infiltrating the soil and becoming available to plants.

ARS is the U.S. Department of Agriculture's chief scientific research agency.