X-ray micro-computed tomography characterized soil pore network as influenced by long-term application of manure and fertilizer

Abstract

Manure is used to enhance soil organic matter content, aggregation, and hence porosity. However, knowledge of long-term application of cattle manure and fertilizer impacts on soil porosity at a microscale under corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation is limited. The X-ray microtomography (μCT) is a novel technique that can provide valuable information about the micromorphological features of soil and, thus, can provide important insight into how manure and inorganic fertilization affect soil pore system. In this study, µCT technique was employed to evaluate the changes in soil pore structure caused by the application of manure and inorganic fertilizer on the surface soils cultivated under corn-soybean rotation. Soil cores were extracted from three treatments viz., dairy cattle manure (DM), inorganic fertilizer (IF) and control (CNT), arranged in a randomized complete block design with three replications. Cores were scanned at a voxel resolution of 31.6 µm and image visualization, processing and analysis were performed using ImageJ software. Application of DM significantly enhanced soil organic carbon (P < 0.001) and CT-measured porosity (0.079 mm3 mm−3) compared to the CNT (0.031 mm3 mm−3), however, these parameters were similar between IF and CNT. Higher porosity in DM enhanced saturated hydraulic conductivity compared to the IF and CNT.The largest contribution to the porosity was from the pores > 100 mm3 for all the treatments.However, microstructural pore properties were mostly similar between IF and CNT treatments. This study highlighted the importance of X-ray microtomography technique in quantifying the soil pore structure and indicated the improvement in the microscopic soil physical environment with long-term application of dairy manure.