Work

Quantifying and visualizing soil macroaggregate pore structure and particulate organic matter in a Vertisol under various straw return practices using X-ray computed tomography

Year: 2024

Type: article

Abstract: Protection of particulate organic matter (POM) within soil aggregates is a key mechanism for carbon sequestration in soil. Combining X-ray CT imaging with other analytical techniques offers numerous opportunities for the nondestructive determination of POM within intact macroaggregates; however, these approaches still make image segmentation a challenging task. The study aims to develop a procedure for quantifying and visualizing POM within intact soil macroaggregates using X-ray CT imaging combined with machine learning techniques, and to test the performance of the proposed procedure under different straw return practices: no-tillage with straw mulching (NTS), traditional rotary tillage with straw incorporation (RTS), and deep plowing with straw incorporation (DTS), in a Vertisol. We analyzed 27 soil aggregates (4-6 mm) collected across soil depths (0-10, 10-20, and 20-40 cm) and scanned them at an 8-μm resolution. The POM quantified within the macroaggregates using our procedure showed a strong correlation with traditional laboratory measurements (R2 = 0.939). The NTS treatment significantly increased POM content by 54.4% in the 0-10 cm soil layer compared to RTS, while the DPS treatment maintained high POM levels in the 20-40 cm layer, with a 278% increase. Additionally, the DPS treatment resulted in the most extensive and well-connected pore networks, particularly in the deeper soil layers, and significantly increased aggregate porosity in the 20-40 cm layer. Furthermore, DPS exhibited the highest POM proportion and volume density in connected pores, with a strong positive correlation between POM content in connected pores and connected porosity (R² = 0.713, P < 0.01), highlighting the importance of pore connectivity in enhancing soil organic matter accumulation.

Source: Geoderma

DOI: 10.1016/j.geoderma.2024.117105

Authors: Zichun Guo, Tianyu Ding, Yuekai Wang, Ping Zhang, Lei Gao, Xinhua Peng