LONG-TERM TILLAGE EFFECTS ON PHYSICAL PROPERTIES OF ERODED SOIL

Abstract

Conservation tillage protects the soil from erosion, but it can result in soil compaction and higher bulk density. This corn-soybean rotation study was 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 soil in southern Illinois. The soil with the NT system had higher water contents 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 residue coverage and water-filled porosity. During the long-term study, nonsignificant differences attributable to tillage were observed at 25 days after planting in average clod bulk density (33 kPa). However, the 8-year average core bulk density was 1.39, 1.32, and 1.31 Mg/m³ with NT, CP and MP systems, respectively, with NT significantly higher than either CP or MP. Higher 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 density clearly affected our results, which contradict previous findings of other long-term studies on different soil situations. Cone penetration resistance was consistently higher with the NT system at 8-cm depth at planting or at 25 days after planting, but resistance values were below root-inhibiting resistance. Moldboard plowing resulted in a tillage-induced traffic pan immediately below the plow depth. No-till increased the water-filled porosity because of the maintenance of soil aggregate stability, but the lack of tillage resulted in decreased air-filled porosity with time. Bulk density, cone penetration, and porosity results from this study contradict previous results from uneroded soils at almost level sites but support other findings from other studies. The interaction between tillage and soil erosion resulted in either different findings and/or impacted the trend and magnitude of the soil property differences between treatments. The NT system performed better than the MP system for soil water storage but failed to maintain macroporosity and resulted in higher bulk density in the surface layer.