How can pore characteristics of soil aggregates from contrasting tillage systems affect their intrinsic permeability and hydraulic conductivity?

Abstract

Studies on how the alteration in the soil pore architecture can influence the permeability of small soil aggregates are still scarce. These aggregates affect the water dynamics mainly at the intra-aggregate pore scale. Thus, investigating the intra-aggregate pore space properties becomes crucial for comprehending the matter and energy transported into the soil. This paper focuses on analyzing the permeability and hydraulic conductivity of small soil aggregates from contrasting tillage systems (no-tillage – NT, minimum tillage – MT, conventional tillage – CT, and secondary forest – F) through synchrotron-based X-ray Computed Tomography. The 3D image segmentation was performed using machine and deep learning strategies. Permeability was measured based on the image-based parametrization of the Kozeny-Carman equation, which is dependent on porosity, hydraulic radius, and tortuosity. The porosity, hydraulic radius, and pore connectivity were not affected by the soil tillage systems at the scale of analysis (aggregates of a few millimeters). Conventional tillage had higher pore tortuosity relative to NT, demonstrating less favorable fluid transport at the aggregate scale. However, only the aggregates under F had significantly higher permeability and hydraulic conductivity relative to NT, MT, and CT. Our results brought new insights into the effects of different tillage systems on the soil structure and their possible impact on water dynamics at the microscale.