Long-Term Interactive Impact of Cover Crop and No-Tillage on Soil Hydro-Physical Quality, N-Fertilizer Demand and Rainfed Cotton Yield.

In sub-humid mid-south US, substantial amount of the cotton residue may decompose within a short period after harvest. This effect influences the rate of no-till induced alterations on soil physical properties. Inclusion of cover crops (CCs) may be an appropriate intensive enhancing the potential of no-tillage. Accordingly, we examined thirty-five years of interactive Impact of two tillage managements; (CT; chisel plow), (NT; no-tillage) and three cover crops; no cover crop (NCC) with 101 kg N ha^-1, hairy vetch (VCC) with 34 kg N ha^-1, and winter wheat (WCC) with 101 kg N ha^-1, on soil hydro-physical properties and cotton yield on a Lexington silt loam in 2015 and 2016. Soil samples were collected in two depth increments between 0-300mm and tested in laboratory or examined in the field for dry bulk density (BD), cone penetration resistance (CPR), soil water content (SWC), water retention characteristics (SWRC), pore size distribution (PSD), wet aggregates stability (WAS), aggregate size distribution (ASD), water infiltration properties and field saturated hydraulic conductivity. Dry bulk density and cone penetration resistance were not affected by tillage and CC before the annual plow application on CT. In general, NT and VCC significantly increased the WAS, soil moisture content at low water potentials, mean weight diameter, FC moisture content, initial infiltration rate and field saturated hydraulic conductivity mainly at 0-15cm soil depth. WCC engendered intermediate effect among cover crop managements. PSD derived from soil water retention curve SWRC showed a hierarchical and multi modal structure of pore space with separated structural and matrix domains. NT at top layers; 0-7.5 and 7.5-15cm resulted in a lower structural and higher matrix porosity compared to CT. Result suggest that cover crops and particularly legume VCC can increase the positive effect of NT on soil hydro-physical quality while decreasing the dependency on nitrogen fertilizer.