DURATION AND EFFECTS OF COMPACTION ON SOIL AND PLANT-GROWTH IN WISCONSIN

Compaction by 8 and 12.5 Mg farm equipment caused significant subsoil compaction that persisted after 4 years in a silty clay and a silt loa m soil in Wisconsin, USA. Hydraulic conductivity of saturated soil cor es showed a general trend of decreasing with increasing levels of comp action. Bulk density values increased with increasing levels of compac tion. Penetration resistance dramatically increased with increasing le vels of compaction. Corn growth (plant height) was also a good indicat or of compaction. Plant height was smaller in the compacted plots in a ll years. Corn grain yields were reduced in the compaction treatments the first year after compaction at both sites and the second and fourt h years at the silt loam site and silty clay site, respectively.