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 loam soil in Wisconsin, USA. Hydraulic conductivity of saturated soil cores showed a general trend of decreasing with increasing levels of compaction. Bulk density values increased with increasing levels of compaction. Penetration resistance dramatically increased with increasing levels of compaction. Corn growth (plant height) was also a good indicator of compaction. Plant height was smaller in the compacted plots in all years. Corn grain yields were reduced in the compaction treatments the first year after compaction at both sites and the second and fourth years at the silt loam site and silty clay site, respectively.