Submitted to: International Soil Tillage Research Organization Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 26, 1999
Publication Date: N/A
Technical Abstract: The size of farming units of North America continues to increase, forcing farm managers to use larger field equipment to perform field operations in a timely manner. In the northern latitudes where impending winter conditions force farmers to harvest as soon as the crop is mature, regardless of soil conditions, it is often necessary to operate heavy field equipment when the soil is quite wet and easily deformed. This paper summarizes several years of field experiments in Minnesota, Wisconsin and Quebec. Plots were compacted track by track until the entire plot surface was covered with wheel traffic carrying axle loads ranging from 7-18 Mg, typical for maize harvesting equipment. This wheel traffic was applied only at the beginning of the long-term field experiments, after which all wheel traffic on the plots was limited to 5 Mg per axle or less. The surface 0.25 m of the soil was then intensively tilled to remove surface compaction. The objectives were to (1) measure extent, depth and persistence of changes in soil physical properties from heavy wheel traffic, and (2) measure effects of any subsoil compaction on yield of maize. High axle load wheel traffic altered physical properties in the subsoil to a depth of at least 0.6 m. Depending on location, significant reductions in maize yield (up to 55%) were measured the first growing season after the initial application of high compaction forces. There was long-term residual subsoil compaction that affected maize yield, the magnitude of which depended on soil type and climatic factors. Natural forces (freezing and thawing, wetting and drying) did not completely ameliorate subsoil compaction. Fields subjected to annual heavy wheel traffic may suffer a permanent maize yield reduction.