Soft X-ray radiography of structure-induced macropore flow in clayey soils

摘要

Soft X-ray radiography was performed in combination with saturated hydraulic conductivity and outflow experiments to characterize structure-induced macropore flow in agriculture field soils. Image analysis showed that isolated cylindrical macropore paths were predominant in paddy soils and tortuous networked macropore flow paths were observed in upland field soils. Interaggregate macropore flow paths were also found in upland field soils. Numerical analysis revealed the presence of discontinuity in hydraulic conductivity near saturation, which is small in loamy soils and large in clayey soils. Interaggregate macropore might lessen the discontinuity at near saturation. Therefore, the domain was divided into two (cylindrical macropore and matrix) in clayey paddy soils and into three (cylindrical macropore, interaggregate macropore, and matrix) in loamy upland field soils. Macropore flow in clayey paddy soils might conduct water and solutes to a lower profile with few interactions with bulk soils.