Submitted to: Seasonally Frozen Soils Symposium
Publication Type: Proceedings
Publication Acceptance Date: June 12, 1997
Publication Date: N/A
Interpretive Summary: Compaction is a concern for the long-term productivity of soils. Compaction can cause crop yield depressions either through limiting root exploration, restricting seedling emergence, or affecting root-water or root-oxygen exchange. Little is known about the persistence of compaction from heavy vehicle traffic, or about environmental factors which ameliorate compaction. Past research indicates that surface compaction may be ameliorated to some extent after one winter in Minnesota. However, subsoil compaction has persisted for a decade in regions where soils freeze. Compaction was evident on an old pioneer trail in Minnesota, some 100 years after traffic ceased along the trail. Compacted soils in the wheel ruts reduced gas exchange and water infiltration by 50%. Because soil compaction can last for a century or longer, farmers can use this knowledge as an incentive to restrict wheel traffic on fields in order to curtail the threat of loss of crop productivity from compaction.
Technical Abstract: Large tractors and implements driven over wet soils can cause compaction, a concern for long-term productivity of fine-textured soils. Past studies related to amelioration of compaction from soil processes such as wetting and drying and freezing and thawing suggest that subsoil compaction can persist for years. Indeed, Swedish experiments ascertained that subsoil compaction can persist over 11 years despite annual freezing below the depth of compaction. A paucity of information exists, however, on the persistence of compaction beyond a decade. Wagon wheel ruts are yet evident along some pioneer trails that traversed the continental United States in the late 1800's, suggesting that compaction can persist for over a century. One such trail, the Wadsworth Trail that traversed western Minnesota from 1864 to 1871, was the focus of this investigation where we examined the soil physical properties across a spur of the Trail. Physical properties assessed across the spur included soil water content, thermal conductivity, penetration resistance, water infiltration, and air permeability. Soil density appeared greater within the area occupied by the wheel ruts compared to that outside the wheel track due to higher penetration resistance and lower water and air infiltration. Indeed, complete amelioration of physical properties that characterize compacted soils were not evident after at least 85 years. This information suggests that for a sustainable agricultural system, compaction of soils should be minimized by either using confined wheel traffic patterns or curtailing traffic on wet soils.