Dynamics of pore functions and gas transport parameters in artificially ameliorated soils due to static and cyclic loading

Soil compaction is one of the main threats to sustain soil quality in modern agriculture. To improve our understanding concerning the interaction between soil physical properties and stress-strain on pore functions and soil aeration, measurements were performed with three different textures (sand, silt loam, clay loam), two matric potentials (−60 and −300 hPa), three compaction levels (50, 100 and 200 kPa) and two loading types (static and cyclic loading). Soil compaction led to a reduction in air-filled porosity εa, air permeability Ka, and relative gas diffusivity Ds/Do. The differences in Ka and Ds/Do among various treatments depend on the remaining air-filled porosity, pore continuity, and pore tortuosity. The water blockage effect on Ka and Ds/Do with lower εa also should be considered sometimes after compaction. The question of how far the compacted and deformed soils can be ameliorated was tested in the same set of samples by artificially prepared five vertical holes. Due to this procedure of vertically arranged continuous and non-tortuous holes in the samples, the values of Ka even significantly increased up to more than one order of magnitude, and the values of Ds/Do also increased obviously, even though the volume of air-filled pores only increased slightly. This situation was mainly attributable to the significant increase in pore continuity and a decrease in pore tortuosity compared to without vertical holes. We also found that there were minor differences on Ka but distinct differences on Ds/Do among all treatments after having drilled vertical holes.