Lime application effects on soil aggregate properties: Use of the mean weight diameter and synchrotron-based X-ray mu CT techniques

Abstract

The hierarchical organization of aggregates in soil is responsible for the presence of inter and intra-aggregate pores. This research aimed to investigate effects of soil surface liming, considering lime rates of 0, 10 and 15 t ha(-1), on the intra-aggregate porous system of soil aggregates with equivalent diameters of 2-4 and 1-2 mm, from 0 to 10 (A) and 10 to 20 cm (B) soil layers. These aggregates were selected by the wet sieving method carried out for determination of the mean weight diameter. Synchrotron-based computed microtomography (mu CT) of aggregates was analyzed in terms of porosity, connectivity, tortuosity, and fractal dimension. Additionally, X-ray fluorescence was used to evaluate the elemental composition of the soil aggregates. All liming effects were concentrated at layer A, where calcium percentage was elevated in aggregates from 1-2 mm class as compared to those from 2-4 mm class. Accordingly, the physical parameters studied were generally more affected in the case of smaller aggregates (1-2 mm). Liming decreased total porosity, increased tortuosity of pores, and decreased fractal dimension for 1-2 mm aggregates, which was in line with the fact that larger pores were replaced by smaller ones in 1-2 mm aggregates, as found via both quantitative and qualitative analyses. On the other hand, liming did not affect pore connectivity under any of the circumstances