Compacted subsoil remediation by soybean cultivars and cotton: A multi-season quantitative study with X-ray computed tomography

• Soybean cultivars resist soil compaction differently. • Multi-scale soil structural was characterized using dual-source X-ray CT. • Sub-compacted soil structure was improved variably across plant types and soybean cultivars. • X-ray CT uncovered macroporosity peaks and layered pores despite standard soil preparation. Soil compaction poses a significant challenge to crop growth, particularly in regions with intensive agricultural practices. Soybean as a taproot crop, is expected to exhibit significant potential for ameliorating compacted soils; however, relevant research remains limited, especially among soybean cultivars. We evaluated the resistance of four soybean cultivars (QH34, Z1307, ZH301, ZH13) and cotton to subsoil compaction by analysing root traits, alongside their capacity to remediate compacted soil structure over two growing seasons in the Huang-Huai-Hai region. Soil structure was evaluated using dual-source (medical/industrial) X-ray computed tomography (X-ray CT) in multi-scale (core/column). Results revealed no significant differences in aboveground biomass between compacted and non-compacted treatments across all cultivars. However, root biomass in the compacted layer (15–45 cm) showed marked variations: cotton, Z1307, ZH301, and ZH13 exhibited no significant reduction, while QH34 displayed a significant decrease, reflecting its lower resistance to soil compaction. This reduced resistance in QH34 corresponded to a lower saturated hydraulic conductivity (Ks) in the compacted layer. Soil water content was higher in compacted treatments, likely due to decreased root water uptake. Furthermore, medical X-ray CT analysis demonstrated that cotton, Z1307, and ZH13 significantly improved macropore continuity and vertical connectivity in the sub-compacted soil after two growing seasons. These findings highlight the differential compaction resistance among soybean cultivars and their remediation ability of compacted subsoil by soybean cultivars and cotton.