Runoff, sediment and nutrient losses from various tillage systems of cotton

Abstract

Runoff, sediment and nutrient losses were studied from 3 tillage systems of cotton ( Gossypium hirsutum L. ‘McNair 235’): (1) no-till without a cover crop (NT); (2) reduced-till with a winter wheat ( Triticum aestivum L. ‘Coker 747’) as a cover crop (RTC); (3) conventional-till (CT) in the Tennessee Valley of north Alabama during the 1985 growing season. Runoff samples were collected from natural rainfall events and analyzed for sediment and nutrient losses. Among the 3 tillage systems the RTC system was the most effective in reducing the surface runoff, sediment and nutrient losses while maintaining comparable crop yield. Runoff and sediment concentrations from the CT system were high during the “critical period” (from planting to the last cultivation of the CT system). During the “non-critical period” (between the last cultivation of the CT system to harvesting) sediment concentrations from all tillage systems were relatively low even with high-runoff events. Summer cultivations reduced both surface runoff and sediment concentrations from the CT system. This may signify that a combination of conservation tillage and summer cultivation has the potential for controlling weeds without enhancing soil erosion. Concentration of ammonium nitrogen (NH 4-N) and soluble-phosphorus concentration in surface runoff were higher than the recommended standard level for public water supplies and the growth of algae, respectively. Concentration of nitrate nitrogen (NO 3-N) in the surface runoff was well within the upper limit for drinking water.