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Description and modeling of the impacts of rigid calcareous concretions and shrinkage on the water retention curve of a Vertisol
Soil and Tillage Research ( IF 6.5 ) Pub Date : 2024-02-13 , DOI: 10.1016/j.still.2024.106039 Y.M. Chen , Z.C. Guo , L. Gao , Y.Q. Qian , Z.B. Zhang , X.H. Peng
Soil and Tillage Research ( IF 6.5 ) Pub Date : 2024-02-13 , DOI: 10.1016/j.still.2024.106039 Y.M. Chen , Z.C. Guo , L. Gao , Y.Q. Qian , Z.B. Zhang , X.H. Peng
Calcic Vertisol, locally called as Shajiang black soil in China, contains numerous porous and rigid calcareous concretions (CCs). However, the impact of CCs on the water retention capacity of Vertisols is not fully understood. The objectives of this study were i) to quantify the effects of the CC content and size distribution on soil water retention and ii) to develop a model to characterize the relationship among the CC content (), water potential (), and soil water content (θ) considering soil shrinkage. The CCs in different sizes (2–5, 5–10, 10–20, and 20–30 mm) or different contents (0, 5%, 10%, and 20% on mass) were mixed with fine soils (<2 mm) to form CC–soil mixtures. The impact of CCs on the water retention curves (WRCs) of the CC–soil mixture was measured. Our results showed that the saturated water content () of CCs decreased from 0.270 to 0.166 cm cm or that the bulk density increased from 2.00 to 2.23 g cm as the CC size increased from 2–5 to 20–30 mm, yielding different water retention properties from that of fine soil. Compared to fine soil, the WRC parameter increased and decreased of the CC-soil mixtures with increasing CC content or size. Moreover, or the void ratio () of the mixtures significantly decreased with increasing CC content ( < 0.05), which was not observed for the CC size. The contribution of CCs to water retention increased with increasing CC content or decreasing CC size. We developed a new numerical equation based on the van Genuchten (VG) model to capture the relationship among ––. The WRCs of the CCsoil mixtures were accurately predicted ( = 0.909–0.953) using the individual WRCs of fine soil and CCs with shrinkage correction for bulk soil. However, the proposed model overestimated the water content on the dry side of the WRC, in which the fine soil volume change among CCs was partially concealed. This work improves our knowledge of the response of water retention to the presence of rigid coarse inclusions in non-rigid soils.
更新日期：2024-02-13
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