Natural freezing processes as a nature-based solution to alleviate soil compaction

Soil compaction consistently ranks among the top three soil degradation processes, becoming a severe, invisible and long-standing threat for sustainable agriculture with intensified machinery operations, leading to a 6–13% loss in yield worldwide. However, large-scale, cost-effective, and efficient alleviation of soil compaction remain challenging. It is noteworthy that freezing induced water redistribution toward freezing front and phase change of accumulated water to ice (sometimes greater than porosity) during soil freezing would significantly improve soil structure by reducing bulk density (BD) or soil penetration resistance (SPR). As 75% of the terrestrial land in the Northern Hemisphere is subject to seasonal freeze-thaw cycles that could be a promising nature-based solution for soil compaction alleviation, but its effects exhibit complex temporal and spatial heterogeneity. Therefore, we conducted a meta-analysis of 822 paired observations from 31 global studies to elucidate the effect and extent of freeze-thaw process on soil compaction relief. The results show that freeze-thaw cycles significantly decreased BD (-5.4%) and SPR (-38.7%), with maximal efficacy in the 0–50 cm profile (BD reduction: −7.7% at 0–10 cm; SPR reduction: −49.3% at 0–10 cm). Initial BD (prior to freezing), initial soil water content, and clay content are the main controlling factors. Remediation efficiency increased proportionally with higher initial BD and SPR values. No-tillage achieves the optimal effect of freeze-thaw process on soil compaction relief by maintaining pore connectivity and aggregate stability (BD reduction of −9.0% compared to −2.3% in control). In addition, Python module for Symbolic Regression and the Symbolic Regression algorithm were combined to model the mitigation effects of freeze-thaw processes on soil compaction in global croplands under different scenarios. The results showed that proper agricultural practices (e.g., irrigation before winter or conservation tillage) may be a cost-effective and extension approach to improve structure of compacted soils. • Freeze-thaw (FT) processes can effectively reduce bulk density and soil penetration resistance of top 50 cm • FT processes induced soil structure recovery are most effective in no-till soil • Soil compaction mitigation is driven by initial bulk density, water and clay content