Gypsum (CaSO4·2H2O) has a wide range of agronomic and environmental applications because of its favorable effect on both soil physical and chemical properties. Regular use of gypsum to the most sustainability of irrigated soils is essential. Earlier researches concluded that gypsum use worldwide was limited to reclamation of sodic soils or as a nutrient source for Ca or S, but current studies suggest potential for use on slightly dispersed and highly acid soils. Also gypsum may significantly increase water infiltration, plant emergence, or both, and prove to be at least a short-term solution to yield reductions, particularly in semiarid or marginal rainfall areas.
Gypsum application can improve root system establishment in low Ca and high Al soils resulting in higher nutrient uptake and greater yields. The combination of effect on some soils may improve yields and production efficiency synergistically by allowing more water to infiltrate and allowing roots to exploit water that is stored in subsoil horizons.
Clearly, gypsum application to soils can have a multitude of impacts on both chemical and physical properties, which can ultimately affect crop production and environmental quality. Many researchers have shown that gypsum can be used as a soil conditioner to improve physical and chemical properties by promoting better aggregation, increasing water infiltration rate and movement through the profile, reclaiming sodic soils, mitigating subsoil acidity and aluminum (Al) toxicity and reducing soil and soluble phosphorus (P) loss from agricultural fields.
Shortage of fresh water is becoming a main constraint to irrigated agriculture through the world. In the past years, over exploitation of ground water for agricultural irrigation is leads to declining in ground water level, increasing soil salinity and decreasing water quantity. It has been estimated that worldwide 20% of total cultivated land, 33% of irrigated agricultural lands are affected by high salinity.
However, continuous irrigation with saline water often leads to adverse effects on crop growth, because salts may gradually accumulate in the root zone. Application of agriculture gypsum is an efficient agricultural practice used to reduce salt stress and improve crop growth in salt-affected areas.
Gypsum has been applied to agricultural soils for more than 250 years in those crops which have high Ca requirements, or to areas that have Ca poor soils since it is an excellent source of soluble Ca and S. Root and field crops such as peanut, potato, tomato, corn, wheat, etc. seem to especially respond to Ca, and application of agriculture gypsum can improve both yield and quality of products.
Similarly, S fertilization is required for many crops, such as alfalfa, soybean, canola, etc., and application of agriculture gypsum can be an effective source of S. In general, crops grown on soil with low organic matter and coarse-textured can respond to S application.
Gypsum also can improved nutrient availability. The application of gypsum in soils increases the sorption activity of Ca2+ and (SO42–) by plants, and results in improvement of nitrogen (N) uptake. This may reduce the need to apply more N to the plants, as well as diminish the potential for nitrate (NO3 –) contamination of surface and ground waters.