|Smith Jr, Sammie|
Submitted to: Mississippi Water Resources Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 1, 1995
Publication Date: N/A
Interpretive Summary: Controlling soil erosion and resulting sedimentation problems in aqueous ecosystems surrounding agricultural lands has led to the increased adoption of no-till (NT) and other reduced tillage (RT) practices. Such practices require an increased use of herbicides to control weeds that are usually controlled with conventional tillage (CT). Increased infiltration generally associated with NT and RT is of concern because of the potential increased threat of contamination of our Nation's ground water with agrichemicals. Fertilizer and pesticide movement in runoff and shallow ground water was determined and compared for three tillage practices in corn grown on the loessial uplands of northern Mississippi. Amount and distribution of rainfall rather than tillage system were found to be the most common factors in influencing agrichemical movement from the corn systems in this study. This information provides the NRCS with additional guidance for making sediment/pesticide management recommendations to farmers.
Technical Abstract: Agrichemical transport and losses were evaluated in corn systems on fragipan soils in the uplands of northern Mississippi during a four year period. Pesticides and nutrients were measured in runoff and shallow (< 3 m) ground water from no-till (NT), conventional-till (CT), and reduced- till (RT) corn plots in loessial deposits from 1990 through 1994. Assessments of surface runoff and subsurface drainage at top surface of fragipan layer were evaluated. Atrazine, alachlor, cyanazine, chlorpyrifos, and tefluthrin appeared in both water and sediment phases of the first runoff after application, and the three herbicides appeared in first shallow ground water after application. NT and RT reduced runoff losses of herbicides but increased infiltration. Annual mean nitrate concentrations in shallow ground water for all corn tillage systems were below the EPA maximum allowable drinking water quality standard of 10 ppm. Tillage differences in study apparently do not affect the mean concentrations of plant nutrients in shallow ground water. Water movement was insignificant at fragipan's surface during cropping season for all tillage systems. NT yielded higher soil moistures in root zone for longer periods during cropping season compared to CT. Amount and distribution of rainfall rather than tillage system were found to be the most common factor in influencing agrichemical movement from the corn systems for this region.