|Smith Jr, Sammie|
Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 12/15/1995
Publication Date: N/A
Interpretive Summary: No-till and reduced-till cropping systems for erosion control usually leads to increase quantities of herbicides for weed control as compared to that used with conventional-till systems. Furthermore, increased water infiltration associated with conservation tillage systems as compared to conventional tillage system on soils with hard pans near the surface may have the potential for an increase in ground water contamination. This study in north Mississippi from 1991 to 1994 showed that conservation tillage practices for corn did not significantly increase agrichemical contamination of the shallow ground water, however, the increased water infiltration during the summer time contributed to increased atrazine level following runoff events early in the growing season. Even though ground water was near saturation during the winter months for all tillage practices, no agrichemical effect resulting from tillage practices was found due to a lack of chemical applications during the winter months. These research results are important because they show that distribution and varying amounts of rainfall throughout the different seasons of the year may decrease or increase the effects tillage practices have on ground water contamination. Information from this study provides the NRCS with additional guidance for making pesticide management recommendations to farmers.
Technical Abstract: Highlights of water movement and water quality research in corn tillage studies at the Mississippi Agricultural and Forestry Experiment Station near Holly Springs over the past five years are presented. Agrichemical transport and losses were evaluated in runoff and shallow ground water from no-till (NT), conventional-till (CT), and reduced-till (RT) corn plots on fragipan soils. Results included low soil erosion rates found from NT corn plots and insignificant free water quantities at the fragipan's surface during the cropping season for all tillage systems with limited downward or lateral water movement and, thus agrichemical movement. Maximum ground water movement with the fragipan occurred during the non-cropping season under soil profile saturation. Amount and distribution of rainfall rather than tillage system primarily influenced agrichemical movement from corn systems in this region. Preliminary results indicate that conservation tillage (NT or RT) has limited detrimental effects to water quality in runoff and shallow groundwater and promote better soil water from crop utilization during the growing season.