Tillage and timing of manure application impacts on water quality in karst terrains

Concerns have been raised on the effect of surface application of manure in conservation tillage practices on surface and subsurface water quality. This study evaluated tillage and liquid dairy manure interactions on both surface and subsurface water quality and on corn yield from steep landscapes in the karst terrains of the upper Midwest. The tillage {09}treatments were chisel plow and no-till. The manure treatments were no manure, fall land winter manure application. The results showed that water percolation in these soils {09}occurred mostly through earthworm burrows, root channels and interpedal voids. Tillage {09}had no significant influence on water percolation but manure application increased water {09}percolation. For 60 cm depth, percolation was higher during the non-rowing season than {09}during the growing season. However, there was no difference in water percolation between fall and winter applied manure treatments. Although most of the water flow to samplers {09}was vertical however there was a significant contribution of lateral flow at 120 cm depth {09}samplers due to the presence of an impeding layer. Mineral-N losses by leaching were {09}greatest during the non-growing season. Manure application increased mineral-N leaching {09}compared to no manure but there was no difference in mineral-N leaching between fall and {09}winter applied manure treatments. Mineral-N losses in runoff were not significantly {09}influenced by tillage or manure application. Nitrate concentrations in leachate were mostly {09}above the EPA maximum drinking water standard of 10 mg L-1 whereas nitrate concentration in surface runoff exceeded the standard only a few times. Chisel plow had {09}significantly higher mineral-N leaching than no-till. No-till had significantly higher annual DMRP losses in runoff than chisel plow. Corn yields were higher from chisel than no-till treatment. Fall and winter application of manure equally increased corn yields as compared to no manure treatment.