A meta-analysis of the impact of traffic-induced compaction on soil physical properties and grain yield

Soil compaction caused by wheel traffic is a major driver of soil degradation in modern agriculture and thus, a threat to agricultural sustainability. To improve the predictive capacity of compaction models and to support decision-making that implements site-specific practices for ameliorating soil compaction effects in modern agriculture, we need quantitative syntheses of the effect of soil compaction on soil physical properties and crop types. In this work, we used a meta-analytical approach to summarize results from 51 published articles on the impacts of soil compaction attributed to machinery axle load, wheel passes, compaction events and tire inflation pressure on soil bulk density (rho b), degree of compactness (DC), penetration resistance (PR), volume of water filled pores at field capacity (theta(Fc)), air permeability (k(a)) at field capacity, saturated hydraulic conductivity (k(sat)), and grain yield of corn (Zea mays L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and soybean (Glycine max L.). Results from this meta-analysis (MA) showed that compaction increased soil mechanical strength shown by increased soil rho b, DC and PR. However, an increase in soil strength was more pronounced in the medium- and coarse-textured soils, and mainly in the topsoil (0-30 cm depth). Penetration resistance for the non-compacted soil (control) treatment was 1.21 MPa for the coarse-textured, 1.11 MPa for the medium-textured and 0.93 MPa for the fine-textured soils. Soil compaction on average, increased PR by 99, 94 and by 41 percent in the medium-, coarse- and fine-textured soils. Compaction decreased hydraulic conductivity characterized by k(a) and k(sat) from the topsoil down to the subsoil (>40 cm depth), and grain yield of corn, wheat, barley, and soybean. Overall, compaction decreased grain yield on average by 6-34 percent. Findings of the MA suggest that soil hydraulic properties may be more sensitive indicators to reflect the impact of soil compaction on soil structure and pore system functions in the soil profile. Future efforts should place a greater emphasis on the publication of complete metadata that allows replication and accurate comparison of results across studies and on providing open access to original datasets that can be used to improve our understanding of the effect of traffic-induced compaction on soil functioning, including crop production.

Automated summary

Soil compaction increases soil mechanical strength, mainly shown by increased soil bulk density, degree of compactness, and penetration resistance. Compaction negatively impacts soil hydraulic properties and crop yield, especially in the topsoil.