Soil compaction varies by crop management system over a claypan soil landscape

While the effects of landscape position (LP) and management practices on soil compaction have been documented as individual factors, limited understanding exists of their interactions. Such understanding is needed to prevent site-specific compaction and to better optimize soil management practices using precision agriculture principles and technologies. The objective of this investigation was to quantify, for a typical claypan soil [Epiaqualfs (USDA); Stagnic Luvisols (WRB)], the impacts and interactions of crop management system and LP on soil compaction as quantified by cone index (CI) and CI-related variables. Cone penetrometer measurements were collected in 2004 at three claypan soil LP (summit, backslope, and footslope) for four different cropping systems [CS; mulch tillage corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] (MTCS), no-tillage corn–soybean (NTCS), no-tillage corn–soybean–wheat (Triticum aestivum L.) (NTCSW), and conservation reserve program (CRP)] that had been in place for more than a decade. Soils were sampled at the same time for soil water content (WC) and soil bulk density (BD) measurements. Mean differences for response variables were examined using F-protected (P ≤ 0.05) LSD values. Cone index averaged over soil depth differed by CS and LP. At the footslope position, CI for the NTCSW CS measured ∼2.0 MPa in the upper 25 cm of soil, and was notably greater than the other management systems. This outcome was attributed to the footslope staying wetter for a longer period during the spring and early summer because of un-removed cover crop plant residues. Wetter soils resulted in vulnerability to compaction during planting and spraying operations. Compaction on CRP was predictably less than the grain CS at all LP because farm machinery traffic only occurred on this system with bi-annual weed mowing during the mid-summer. These findings help bring to light where in claypan soil landscapes certain types of grain crop management will cause significant compaction. These areas could be targeted for further soil strength testing and then, when necessary, appropriate compaction remediation actions.