Long-term tillage effects on physical properties of eroded soil

Conservation tillage protects the soil from erosion, but it can result in s oil compaction and higher bulk density. This corn-soybean rotation study wa s conducted to determine the effect of 8 years of continuous no-till (NT), chisel plow (CP), and moldboard plow (MP) treatments on physical properties of an eroded soil. The study was located on a previously eroded, sloping s oil in southern Illinois. The soil with the NT system had higher water cont ents in the 0- to 15-cm soil layer than the soil with the MP and CP systems . The higher water content with NT treatment was associated with greater re sidue coverage and water-filled porosity. During the long-term study, nonsi gnificant differences attributable to tillage were observed at 25 days afte r planting in average clod bulk density (33 kPa). However, the 8-year avera ge core bulk density was 1.39, 1.32, and 1.31 Mg/m(3) with NT, CP and MP sy stems, respectively, with NT significantly higher than either CP or MP. Hig her bulk density with the NT system than with the MP system was attributed to a lower proportion of macropores. The method used to measure bulk densit y clearly affected our results, which contradict previous findings of other long-term studies on different soil situations. Cone penetration resistanc e was consistently higher with the NT system at 8-cm depth at planting or a t 25 days after planting, but resistance values were below root-inhibiting resistance. Moldboard plowing resulted ill a tillage-induced traffic pan im mediately below the plow depth. No-till increased the water-filled porosity because of the maintenance of soil aggregate stability, but the lack of ti llage resulted in decreased air-filled porosity with time. Bulk density, co ne penetration, and porosity results from this study contradict previous re sults from uneroded soils at almost level sites but support other findings from other studies. The interaction between tillage and soil erosion result ed in either different findings and/or impacted the trend and magnitude of the soil property differences between treatments. The NT system performed b etter than the MP system for soil water storage but failed to maintain macr oporosity and resulted in higher bulk density in the surface layer.