Evaluating the Impact of Gypsum Content on the Physical and Hydraulic Properties of Soils in Arid Regions: A Review

Abstract

Gypsum soils constitute approximately 100 million hectares of the world’s area, and approximately 28% of the ​​Iraq s, area.  Low gypsum content (about 14%) have a positive effect on improving soil properties, if the soil has a high gypsum content it will lead to a deterioration in the physical, chemical and fertility properties. Gypsum affects physical soil properties, water movement and water functions because it is semi-soluble and thus affects plant growth and productivity. Gypsum soils are generally of a fine texture, and the texture of the surface layer is often loam, while the subsurface layer has a clay loam texture. Most gypsum soils are poorly structure in their surface horizons, while the sub surface horizons are structure less, or in the form of individual grains. Gypsum soils have a low ability to retain moisture at high pressures and high temperature conditions. An increase in soil gypsum content reduces organic matter, clay percentage, and available water. As the percentage of gypsum in the soil increases, the bulk density values ​​increase up to 30% gypsum, as well as the value of the liquid, plasticity limits, and plasticity index value decrease. The values ​​of saturated hydraulic conductivity depends on the nature of the gypsum crystals and their percentage in the soil. The rate of water column rise has an inverse relationship with the gypsum percentage. The importance of this study to reduce the deterioration of gypsum soils.