Effects of wheat cover crop desiccation times on soil physical properties and early growth of corn under no-till and conventional tillage systems

Cover crops can improve soil physical properties but can present challenges for subsequent cash crop growth. The objectives of this research were to investigate the influence of a winter wheat (Triticum aestivum) cover crop on selected soil physical properties and early development of corn in a corn (Zea mays)-soybean (Glycine max) crop rotation. The measurements were conducted on two Indiana research farms, both with dominant silt loam soil types during seasons 2000, 2001 and 2002. The experimental design was a split-split plot, with tillage treatment as the main effect (spring disking conventional till (CT) and no-till (NT)), two cash crops as the first split (soybean (B) and corn (C)), and three cover crop treatments as the second split (no cover crop (N), early (E) and regular (R) cover crop desiccation). Soil aggregation was usually increased by either E or R relative to N cover crop, and more consistently so in CT than NT. Both the R and E treatments tended to decrease bulk density, cone resistance and soil temperature, but increase total porosity, air-filled porosity, water retention and vane shear strength in both tillage systems, whereas K _sat tended to improve with E or R cover treatments only in CT. Steady-state infiltration, measured on N and R only, tended to improve with R in both tillage systems. For both tillage treatments, both E and R increased soil water content, when compared with N, except in the case of early spring drought, when R transpired more water than E and was similar in water content to N. In years without early spring drought, early corn shoot and root growth following E in CT was either greater or not different than the other two treatments, whereas in NT the R > E > N pattern was frequently observed. In case of early spring drought, the E treatment on both tillage systems had better corn growth than both R and N treatments. The results suggest that despite generally comparable soil structure improvements by both E and R treatments in both tillage systems, early desiccation is the more desirable treatment prior to corn production due to better soil water conservation in droughty weather.