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Physical Conditions of a Lake Plain Soil as Affected by Deep Tillage and Wheel Traffic

Johnson, B. S., Erickson, A. E., Voorhees, W. B.
Soil Science Society of America journal 1989 v.53 no.5 pp. 1545-1551
A horizons, autumn, clay, internal drainage, lakes, planting, plowing, porosity, saturated hydraulic conductivity, soil compaction, soil density, spring, subsoil, subsoilers, subsoiling, tractors, traffic, Michigan
Normal fall and spring tillage practices create poor physical conditions for crop growth on lake plain soils in Michigan. Charity clay [fine, illitic (calcareous), mesic Aeric Haplaquept] (Mahjoory and Whiteside, 1976) is an example of such a soil. It has poor internal drainage due to its naturally dense subsoil and is susceptible to physical degradation because of its unstable surface. Tillage studies were conducted from 1983 to 1985 to evaluate the potential for reducing the physical limitations of Charity clay. Treatments consisted of four combinations of a primary and secondary tillage variable. The primary tillage variable involved the application or omission of deep tillage using a triple-shanked subsoiler prior to moldboard plowing. The secondary tillage variable involved the presence or absence of tractor wheel traffic prior to planting. Subsoiling improved the physical conditions of Charity clay below the Ap horizon. Soil bulk density (ρb) was reduced by 0.05 Mg m⁻³, and pore size distribution (PSD) was altered such that the volume of pores with radii larger than 150 µm was doubled. Preplant wheel traffic caused subsoil compaction, increasing ρb by about 0.06 Mg m⁻³, and altered all indicators of soil compaction in the Ap horizon, especially PSD and saturated hydraulic conductivity. The need to minimize wheel traffic regardless of the primary tillage practices employed was evidenced by the results of this study. Contribution from the Michigan Agric. Exp. Stn., Michigan State Univ. Partially supported by a grant from the USDA-ARS.