Objective To provide basis for the improvement of saline soil and utilization of coastal reclamation zones, the pore distribution characteristics of soil column under different land use types of coastal reclamation zones were analyzed.

Methods Paddy field and abandoned land of coastal reclamation zones were selected in Chongming, Shanghai, and the pore distribution characteristics of soil column (0 - 35 cm) were quantitatively studied under two different use land types of coastal reclamation zones, by using the soil column computed tomography (CT) technology and image analysis software. At the same time, soil bulk density, total soil porosity, soil aerated porosity, soil capillary porosity, soil saturated water holding capacity, soil capillary holding water capacity and soil field water holding capacity of 5 - 10 cm, 15 - 20 cm, 20 - 25 cm and 30 - 35 cm on the soil profile were measured. Soil compaction and volumetric water content were measured in situ by soil compaction meter and soil sensor.

Results The results showed that there was a heterogeneity for the pore distribution of soil column in paddy field. The more and larger pore distribution was found in the upper soil layer, the less the subsoil layer had pore distribution. The pore distribution of soil column in abandoned land was relatively homogeneous. The connectivity of soil macro-pores in paddy field was relatively poorer, and the macro-pores of the upper soil mostly existed in the form of massive accumulation. The soil macro-pore connectivity in the abandoned land was relatively better, and the vertical tubular structure was obvious. The distribution characteristics of soil macro-pore in paddy field and abandoned land were relevant to soil volumetric water content. Correlation analysis showed that the ratio of total porosity and macro-porosity obtain by CT were negatively correlated with soil bulk density (P < 0.05), and significantly positively correlated with total porosity, soil saturated water holding capacity, soil capillary water holding capacity and soil field water holding capacity (P < 0.05).

Conclusion The soil pore characteristic parameters obtained by soil column CT scanning technology would provide reference for soil improvement in coastal reclamation zones.