Seasonal Hydrologic Impacts of Conservation Tillage for a Coastal Plain Soil

Strip till, a practice of planting into a narrowly tilled strip, is a growing practice among many Coastal Plain cotton growers. Strip tillage increases crop residue at the surface, leading to reduced evaporation and reduced raindrop impact. In many cases increased infiltration, reduced surface runoff, and reduced transport of sediment and agrichemicals are also observed. This research examines nine years of rainfall-runoff data from a paired conventional till / strip till research site. Annual water gains in the strip till system obtained through enhanced infiltration and reduced surface runoff were offset by increased subsurface losses. Strip till had the greatest benefit in terms of increased water gains during years with the least annual precipitation. These results indicate that strip till systems can potentially increase plant available water through enhanced infiltration. This increase is most prevalent during the crop growing season from June through August. Water losses through subsurface flow tend to cancel out any gains obtained through increased infiltration occurring throughout the remainder of the year. On an annual basis, the total water lost as a % of rainfall from the conventional till plots averaged 34% while it averaged 33% for the strip till plots. Of this, the conventional till plots lost 23% through surface runoff and 11% through subsurface losses. For the strip till plots the annual losses were 14% through surface runoff and 19% through subsurface losses.