Compaction of a sandy loam soil not impacted by long-term biosolids applications

Soil compaction and soil organic matter (SOM) are critical factors influencing crop growth and soil health, yet their interaction and impact on plant-available water (PAW) remain underexplored. To address this, we investigated a 26-year field experiment on fine sandy loam soil in Washington State, USA, involving three biosolids application rates (0, 4.7, and 10.0 Mg ha⁻¹) applied every four years in a winter wheat-fallow rotation. Compacted and uncompacted strips were created using field-traffic, with additional intact soil cores from uncompacted strips compacted in the laboratory. Intact cores from uncompacted, field-compacted and lab-compacted treatments were analyzed for saturated hydraulic conductivity ( K sat ), soil moisture release curves, and bulk density (ρ b ). The change in ρ b after compaction (Δρ b ) and rebound (Δε) were assessed for lab-compacted cores. Disturbed soil samples were analyzed for Proctor maximum bulk density (ρ bmax ), critical water content (CWC), and contact angle (α). Biosolids application generally reduced ρ b and ρ bmax , increased CWC, volumetric water content at saturation (θ SAT ), K sat , and α but did not affect volumetric water content at field capacity (θ FC ), permanent wilting point (θ PWP ), or PAW. Compaction reduced θ SAT and K sat while increasing ρ b , θ FC , θ PWP , and PAW. While compaction impacted soil physical and hydraulic properties, biosolids had limited effects under the study conditions. Contrary to our expectations, no interaction between biosolids application and compaction treatments was observed. Despite numerous benefits of increased SOM with biosolids application, increased resistance to and recovery from soil compaction does not appear to be one of them in this study. • Long-term biosolids application did not affect plant available water (PAW). • Compaction-induced changes in bulk density were not affected by biosolids. • Induced soil compaction decreased θ SAT but increased PAW. • Biosolids application did not alter soil’s susceptibility to compaction.