Abstract

Studies on clayey soils developed in temperate areas have shown that their water retention properties are related to both the clay content and the specific pore volume of the clay, the latter being related to the hydric history of the soil, that is to the drying/wetting cycles. Our objective was to discuss the validity of these results for clayey soils developed in semi-arid areas. Samples were collected in soils located in Syria. Physico-chemical properties were determined. Water content was measured at field capacity and for water potentials ranging from −10 to −15,000 hPa. X-ray diffraction analyses were performed on the clay fraction to identify the clay. Results showed that the clays have both a high cation exchange capacity (0.707–0.891 mmol+ g⁻¹ of clay) and a high external specific surface area (112 and 178 m² g⁻¹ of clay). These values are consistent with the X-ray diffraction results which showed the presence of a high proportion of smectite in most horizons and secondarily of varying proportions of illite and chlorite; kaolinite, while present, was not abundant. Results also showed that the amount of water retained by the clay according to the water potential was closely related to the specific pore volume of the clay at field capacity. Regression equations established by using both the data published earlier and those of this study enabled us to predict the water retention properties of clayey soils for a larger range of clay mineralogy and climatic environments including semi-arid environments than previously discussed in the literature.

摘要

对温带地区粘土的研究表明，它们的保水性与粘土含量和粘土的比孔容有关，后者与土壤的含水历史有关，即与干燥/湿润有关。循环。我们的目标是讨论这些结果对半干旱地区开发的粘土的有效性。样本是在位于叙利亚的土壤中收集的。确定了物理化学性质。在现场容量和-10 至-15,000 hPa 的水势范围内测量水含量。对粘土部分进行X射线衍射分析以鉴定粘土。结果表明，粘土具有较高的阳离子交换容量（0.707-0.891 mmol+ g ^-1粘土）和高外部比表面积（112 和 178 m ² g ^-1粘土）。这些值与 X 射线衍射结果一致，该结果表明在大多数地层中存在高比例的蒙脱石，其次是不同比例的伊利石和绿泥石；高岭石虽然存在，但并不丰富。结果还表明，粘土根据水势而保留的水量与粘土在田间容量下的比孔容密切相关。通过使用先前发表的数据和本研究的数据建立的回归方程使我们能够预测粘土矿物学和气候环境（包括半干旱环境）的保水特性，而不是文献中先前讨论的。