Transitioning from conventional to cover crop systems with minimum tillage does not alter nutrient loading

Nutrient loading from conventional row‐crop production systems impairs surface waterbodies in the mid‐southern United States. This study was conducted to determine whether minimum tillage and winter cover crops can decrease nutrient loading in surface runoff from conventionally tilled row‐crop fields. The effects of winter cover crops and minimum tillage on N and P loading from a corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation system were investigated on production fields in northwestern Mississippi using a split‐field approach. As measured at the edge of the field, minimum tillage with cover crops had no effect on surface runoff from production fields regarding N or P loading (p > .10 for all nutrient loads), discharge (p > .10), or loss of suspended solids (p > .10). Minimum tillage and cover crops decreased sediment and nutrient concentrations in runoff for total N (p = .05) and total P (p = .09) but had no effect on other nutrients of interest. Although these practices decreased total N concentration by 36% in surface runoff to receiving waters, this reduction was only seen when aboveground cover crop biomass was present (p = .07). Regardless of the time of year, minimum tillage with cover crops decreased total P concentration in surface runoff by 27% (p = .09). These data indicate that it is unlikely that minimum tillage and cover crops will affect N and P loading while transitioning to a conservation production system in the mid‐southern United States. Core Ideas Cover crops and minimum tillage did not reduce nutrient loading or discharge in mid‐South corn–soybean rotations. Cover crops and minimum tillage reduced total nitrogen concentrations when winter cover was present. Cover crops and minimum tillage reduced total phosphorus concentration when cover was and was not present.