Influence of tillage on maize yield in soil with shallow fragipan

A genuine concern for landowners and other stake holders is whether conservation tillage contaminates shallow groundwater even though it greatly reduces erosion. A six-year continuous maize (Zea mays L.) study that compared yields from no-tillage (NT), reduced-tillage (RT), and conventional-tillage (CT) was conducted in the upland hills of northern Mississippi on 4–6% sloping soils overlying a shallow fragipan. The objective was to test the hypothesis that neither no-tillage nor reduced-tillage has the same effect on maize crop as conventional-tillage on soils with a shallow water restricted layer. The study showed conservation tillage had fewer detrimental effects on the water quality in runoff and shallow groundwater and promoted more soil water for crop use during the growing season than conventional tillage. With adequate weed control, NT produced higher yields than CT on these silt loam soils due to soil water conservation. However, inadequate weed control occurred in several years of the study along with above normal rain resulting in lower NT maize yields than CT yields. Significant differences in maize yield were found for type of tillage, year, and tillage-year interaction. These differences were explained by a tillage system's ability to conserve soil water and control weeds. Other results included low sediment amounts lost from NT maize plots and insignificant free water quantities at the fragipan's surface during the cropping season for all tillage systems. Maximum groundwater movement across the surface of the fragipan occurred during the non-cropping season under soil profile saturation. Amount, timing, and distribution of rainfall rather than tillage system primarily influenced agrichemical movement from maize systems in this study. Some form of conservation tillage that decreases or prevents erosion will be required on sloping lands with shallow fragipan to sustain long term continuous corn production. Information from this study provides additional guidance for making tillage and pesticide management recommendations to farmers.