Hard-setting gypsiferous soils become hard and compact during drying without the impact of soil compaction caused by agricultural field traffic. Thus, these soils are difficult or impossible to cultivate unless they are re-wetted. Moreover, it has previously been shown that Dexter soil physical quality index (S-index) negatively affected by compaction. This study was done to quantify the hard-setting as well as the soil compactness (expressed in terms of the degree of compactness, DC, which is relative density expressed as the ratio of bulk density to a reference density) using water retention data and soil physical quality index of fifteen soils with a wide range of gypsum content (30−301 g kg⁻¹). Repacked soil cores were prepared with less disturbance of soil aggregates ≤ 4 mm). Water retention curves of the soils were measured in the matric suction range 10−15000 hPa. A single-porosity van Genuchten-Mualem model was fitted to water retention data. S-index and Dexter hard-setting (H_Dexter) were calculated using the van Genuchten-Mualem parameters. The relationships between S-index and both DC and H_Dexter were investigated for the 15 gypsiferous soils. A strong positive polynomial and power correlation were found between DC and H_Dexter and S (i.e. 1/S) respectively, and that are valid across different soil gypsum content. Significant negative relationships between H_Dexter and soil gypsum content were observed. Positive polynomial relations were derived between S and bulk density and polynomial relation was obtained between H_Dexter and bulk density. Positive relationships were observed between H_Dexter, DC, and relative bulk density. These findings confirmed that the new proposed H_Dexter index enables the prediction of soil hard-setting behavior to quantify the gypsiferous soil physical quality using only water retention data with no need to measure soil mechanical strength.

坚硬的石膏形土壤在干燥过程中变得坚硬致密，没有农田运输造成的土壤压实影响。因此，除非重新润湿，否则很难或不可能耕种这些土壤。而且，先前已经表明，德克斯特土壤物理质量指数（S-指数）受到压实的负面影响。这项研究使用保水量数据和土壤来量化硬结和土壤密实度（以密实度DC表示，其相对密度表示为堆积密度与参考密度的比值）石膏含量广泛的15种土壤的物理质量指标（30−301 g kg ^-1）。重新包装的土壤芯的制备对土壤聚集体（≤4 mm）的干扰较小。在基质吸力范围10-15000 hPa下测量土壤的保水曲线。将单孔隙率的范Genuchten-Mualem模型拟合到保水数据。使用van Genuchten-Mualem参数计算S指数和Dexter硬定型（H _Dexter）。研究了15种石膏形土壤的S指数与DC和H_德克斯特之间的关系。在DC与H _Dexter和S之间发现强正多项式和功率相关性（即1 / S），并且在不同的土壤石膏含量上均有效。观察到H _Dexter与土壤石膏含量之间的显着负相关。得出S与堆积密度之间的正多项式关系，以及H _Dexter与堆积密度之间的多项式关系。H _Dexter，DC和相对堆积密度之间观察到正相关。这些发现证实，新提议的H_德克斯特指数能够预测土壤硬结行为，从而仅使用保水数据即可定量测定吉普赛土壤的物理质量，而无需测量土壤的机械强度。