Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2009
Publication Date: 12/16/2009
Citation: Jung, K., Kitchen, N.R., Sudduth, K.A., Lee, K., Chung, S. 2009. Soil Compaction Varies by Crop Management System over a Claypan Soil Landscape. Soil and Tillage Research. 107:1-10.
Interpretive Summary: Soil compaction can reduce crop production and further, impair water quality. When soil is compacted, there is less root development, water infiltration, and air movement. Plants stunted by compaction don’t effectively use fertilizer and manure nutrients, and therefore these nutrients become more vulnerable to off-field movement into ground and surface waters. An understanding of the vulnerability of different soils over landscapes to management-induced compaction is needed before we can identify improved sustainable cropping practices. The purpose of this investigation was to measure the impact of crop management systems and landscape position on soil compaction for a poorly-drained Midwest claypan soil. Management systems included both grain and continuous cool-season grass, which represented the USDA Conservation Reserve Program (CRP). As expected, less compaction was found with CRP management because farm machinery traffic only occurred when weeds were mowed on a bi-annual basis. Most significantly we found that when grain crops were managed without tillage and included over-wintering cover crops, the lower portions of the claypan landscape were vulnerable to extreme soil compaction. This happened because these soils were consistently wet when spring operations needed to be performed. We concluded that unless the cover crop could be removed in the early spring to facilitate soil drying before planting, or occasional tillage could be employed to remediate the compaction that developed, use of cover crops in no-till tillage systems was not suitable for these portions of the claypan soil landscape. For the other grain crop production systems and over the different landscape positions, soil compaction values were intermediate, but not at levels that would normally decrease crop growth. Understanding the interactions of tillage and cropping choices over varying landscape positions is crucial to help farmers employ best management practices that prevent compaction. Minimizing soil compaction reduces cropland runoff and thereby benefits the public by preserving stream and lake water quality.
Technical Abstract: While the effects of landscape position 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, the impacts and interactions of crop management system and landscape position on soil compaction as quantified by cone index (CI) and CI-related variables. Cone penetrometer measurements were collected in 2004 at three claypan soil landscape positions (LP; summit, backslope, and footslope) for four different cropping systems [CS; mulch tillage corn-soybean (MTCS), no-tillage corn-soybean (NTCS), no-tillage corn-soybean-wheat (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 an F-protected (P= 0.05) LSD. CI averaged over soil depth differed by CS and LP. At the footslope position, CI for the NTCSW cropping system 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 cropping systems at all landscape positions 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, remediation actions such as site-specific deep tillage.