Submitted to: Soil Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2000
Publication Date: N/A
Interpretive Summary: As size of farms increase, it is necessary for farm operators to use increasing larger capacity machinery in order to get field operations done in a timely manner. This challenge becomes more important in northern latitudes where growing seasons are short. Large capacity farm machinery generally means heavier machinery, especially for harvest and transport equipment. A cooperative international field study was conducted at severa northern European and northern North American sites to determine how deep soil is compacted by the wheel traffic of heavy harvest equipment, how long this compaction persists, and what effects subsoil compaction may have on crop yield. This paper summarizes the studies conducted in North America in Minnesota, Wisconsin and Quebec, Canada. Compaction from a one-time application of heavy wheel traffic extended to depths of at least 2 feet. Corn yields were reduced by as much as 55% the first growing season following heavy wheel traffic. Natural forces such as freezing and thawing tended to alleviate this subsoil compaction but not entirely. Depending on growing season precipitation, corn yields could be significantly decreased up to at least 12 years after the initial heavy wheel traffic. In Minnesota the data suggests an average permanent yield reduction of 6% which amounts to an annual loss of about $20/acre. As we go east to Wisconsin and Quebec where the average growing seasons are wetter, corn yield losses are greater. These data document the need for farmers and the machinery industry to recognize the potential economic trade-off of large capacity farm machinery (which is time-efficient) and possible corn yield losses due to subsoil compaction caused by the heavy machinery. Knowing this, farmers can make a better judgment on how to best use this equipment.
Technical Abstract: The size of farming units in the maize growing region 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.