Traffic-induced soil compaction affects root traits and aboveground biomass of wheat and maize differently

Background and aims Soil trafficking can increase soil compaction in croplands and, thereby, impede root growth and plant productivity. However, the extent to which varying soil trafficking affects soil compaction and, consequently, root depth distribution and biomass productivity is insufficiently quantified. Methods This study investigates the impact of increased traffic intensity on wheat and maize in loamy soils, sampling a gradient with varying traffic intensities. 90 sampling points were randomly placed along headland and in-field areas. Root traits, including volumetric root length density, root dry weight, and the number of roots, were assessed from soil cores up to a depth of 100 cm. Results Higher traffic intensity in headlands significantly increased mean bulk density by 0.07 and 0.05 g cm ^-3 in topsoil (+6%) and subsoil (+3%), respectively. Simultaneously, the soil air capacity decreased by 3.4 and 0.6 vol%. Root dry weight decreased by 43% for wheat, but not significantly for maize (-3%) and the aboveground biomass decreased by 3% in wheat and 6% in maize in headlands compared to in-field areas. No soil physical threshold restricting root growth was observed. Subsoil bulk density and air capacity had a negative, crop- and depth-specific effect on root traits. Root traits at 60–70 cm depth revealed a higher relation with aboveground biomass of wheat, while traits at 30–40 cm depth correlated better with aboveground biomass of maize. Conclusion These findings highlight the need for soil management strategies that minimize soil compaction in order to facilitate root access to subsoil water and nutrient reservoirs.