Effects of Different Compaction Intensities on Soil Microstructure of the Plow Layer

Highlights Soil pore structure and hydraulic parameters were obtained through CT scanning and a ku-pF tester, respectively. Compaction intensity is negatively correlated with the pore branch density (r = -0.65). At 0-15 cm depth, the maximum penetration resistance was a quadratic function with compaction intensity (r2 = 0.89). The slope of the moisture characteristic curve was the greatest when the compaction intensity was 61.5 kPa. ABSTRACT. Soil firming during crop seeding is important in attaining good seed-soil contact and is particularly crucial in arid regions. The theoretical basis for the design of presswheels and similar devices for firming the soil during seeding lies in the study of soil microstructure and water-holding capacity in the plow layer. In this study, we used typical loam from the Northwest China region and soil samples from the plow layer under different compaction intensities. Two-dimensional and three-dimensional models of soil pores were obtained using X-ray computed tomography (CT scanning) and image processing technology. Soil pore structure parameters, such as soil porosity, pore size, and pore quantity, were obtained using ImageJ and Avizo software. Additionally, the aggregate size distribution and moisture characteristic curve were obtained. The results show that (1) Compaction intensity significantly affected soil pore structure parameters, and as compaction intensity increased, the maximum soil cone penetration resistance followed a quadratic function (r 2 = 0.89). (2) Compaction intensity was negatively correlated with pore shape factor (r = -0.69), pore branch density (r = -0.65), and coordination number (r = -0.52). (3) The slope of the moisture characteristic curve was the greatest when the compaction intensity was 61.5 kPa. Compaction intensities within the range of 54.4–68.7 kPa were more conducive to water retention compared to lesser or greater compaction intensities. The results provide technical support for soil structure reconstruction and water migration and a theoretical basis for the selection of compaction intensity applied by presswheels and similar devices for firming the soil during seeding. Keywords: Compaction, Plow layer, Porosity, Soil, X-ray computed tomography.