No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Soil structure and crop response under annual compactive loads of 10 and 18 t/axle and compaction alleviation treatments were assessed in a continuous corn production system. The alleviation treatments consisted of chemical conditioning with a non-ionic surfactant, and subsoiling with narrow-tined and winged implements. Parameters utilized for determining effects on soil structure were bulk density, water retention characteristics and soil profile characteristics. Significant topsoil and subsoil compaction resulted from both loading levels. Crop yield reductions due to compactive loading ranged from 18 to 27% under optimal weather conditions and were as high as 55 to 86% under adverse weather conditions. Soil amendments by chemical conditioning had no beneficial effect on soil structure or crop yields. Inter-row subsoiling with narrow-tined and winged subsoilers was effective in reducing soil compaction and increasing crop yields. / Soil bulk density measurements gave good indication of overall compaction to a depth of 0.4 m and correlated well with crop yields, but were unable to locate differences between compactive treatments. Water retention characteristics indicated significant differences between compactive treatments to a depth of 0.6 m. Soil profile characteristics were useful for determining ped type and size as well as rooting depth and gave the best overall assessment of compaction alleviation effects. / Studies were also conducted to develop a method for predicting soil compactibility that would serve to manage soil compaction at the farm level. Preliminary studies focused on the determination of soil material properties for predicting bulk density changes under applied loads. Further investigations were conducted on the variations in constrained modulus, cone index and soil bulk density values under uniaxial loading. A model relating constrained modulus as a function of cone index, bulk density and soil moisture content was developed. Subsequent studies conducted yielded significant relationships between penetration resistance and soil compactibility as indicated by constrained modulus and coefficient of compressibility. Relationships obtained between penetration resistance and parameters of compactive work and bulk density change indicated the feasibility of assessing soil compactibility at the farm level.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 240-254) Also available in print.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 73-75).

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 124-137).