Conservation tillage dominates pore formation freeze thaw cycles alleviate compaction in northeast China black soil

Conservation tillage (CT) enhances soil structure, but its interaction with freeze-thaw cycles on micropores remains unclear. This field study compared CT and rotary tillage (RT) by using X-ray computer tomography to analyze soil pore characteristics and physical properties. CT promoted large pores (>500 μm) forming stable preferential flow paths, while RT mainly developed medium-sized pores (200-400 μm). Freeze-thaw cycles increased >300 μm porosity by 5%, particularly in the 20-40 cm layer, an effect influenced by bulk density and freezing duration. Soil pore parameters contributed 35% and 48% to soil nutrients in the 0-20 cm and 20-40 cm layers, respectively. Overall, tillage dominates soil porosity formation, and freeze-thaw cycles play a supplementary role in alleviating compaction. These findings provide practical guidelines for integrating CT with natural freeze-thaw processes to sustain black soil health in cold regions.