Short-term effects of overwintering on porosity of the compacted topsoil due to harvest traffic in Northeast China

The multi-hydrothermal processes in agricultural soils during overwintering modify compacted soil structure in cold winter regions. The depth-dependent changes in the topsoil pore-network within field-based compacted zones caused by harvest traffic, before and after winter, remain poorly understood. In this study, we aimed to investigate the short-term effects of overwintering on topsoil porosity of a clay loam soil in the harvest traffic zone in Northeast China using X-ray CT. Undisturbed soil cores were collected in the 0–10 cm layer of the non-traffic and traffic zones before and after winter. After harvest, both total porosity (εtotal) and porosity of > 0.04 mm (εX-ray) significantly decreased by 0.04 and 0.07 cm3 cm−3 due to the machinery traffic, respectively. Following winter, the εtotal of the traffic zone significantly increased by 0.08 cm3 cm−3 and was greater than that of non-traffic zone porosity before winter. The loosening effects of overwintering on compacted soil in the traffic zone diminished with increasing soil depth, and marked alterations limited to the uppermost 3.5 cm. The increase in εX-ray was primarily resulted from the changes in 0.04–1.0 mm pores. Therefore, it is indicated that overwintering can alleviate soil compaction of traffic zone only in the uppermost layer.