Soil structure dynamics in annual croplands under controlled traffic management

Abstract

Soil samples were collected from commercial agriculture sites within western Canada that were subjected to compaction from farm equipment in both conventional (imposed) traffic and controlled traffic regimes. Soil characteristics such as bulk density, pore volume fractions, and unsaturated hydraulic conductivity were compared with soil physical quality parameters, such as S-index and mass fractal aggregation between trafficked and untrafficked field areas. Our results showed that untrafficked soil characteristics displayed substantial improvements over those exposed to equipment compaction. Untrafficked soils in the controlled traffic regime exhibited total porosity improvements up to 15% in more than half of the study sites. In addition, spatial reductions of equipment compaction increased the volume of soil pore diameters associated with preferential water transmission from 40% to 180%. Changes in these soil characteristics within untrafficked soils correlated well with enhancements in the soil structure metrics, as improvements to the S-index were coupled with evidence of hierarchical aggregation. Irrespective of the positive changes to soil structure, significant increases in crop yield were rarely observed in favor of a controlled traffic regime. Our results suggest that the integration of controlled traffic farming into management systems may take several years for the benefits to soil physical quality to translate into observable improvements in crop yield.