Winter-hardy vs. freeze-killed cover crop mixtures before maize in an organic farming system with reduced soil cultivation

The advantages and disadvantages of a winter-hardy vs. a freeze-killed cover crop mixture combined with reduced soil cultivation to a following maize crop were studied on an organic farm in Lower Austria in two consecutive experiments. Effects on soil inorganic nitrogen contents, weed density and the yield of a following maize crop were assessed. The winter-hardy compared with freeze-killed cover crop mixture, both consisting of legumes and non-legumes, reduced soil inorganic nitrogen contents over winter, leading to a reduced nitrate leaching risk, whereas the yield of a following grain maize crop was not significantly affected. Weed density was high in both cover crop treatments, presumably due to the continued reduced, non-inverting soil cultivation on the farm, and higher in the winter-hardy cover crop treatment at one of the assessment dates. Combined with an adapted soil cultivation, both the winter-hardy and the freeze-killed cover crop mixture were suitable before grain maize in this organic farming system with non-inverting soil cultivation under moderately dry site conditions, but the winter-hardy cover crop mixture seems advantageous because it reduces the nitrate leaching risk.