Gypsum for Salt in Soil

About Soil Salinity

• When salts are present in large amounts, they can hinder plant growth. Excessive salinity decreases the amount of water absorbed by plant roots, which can cause drought. According to Alan D. Blaylock of the University of Wyoming Cooperative Extension Service, soil salinity may be caused by improper drainage and irrigation. Saline soils may manifest a crust on the soil surface and often become sticky when they are wet. They may also clump together when dry, which prevents oxygen from reaching plant roots.

About Gypsum

• Gypsum is also known as calcium sulfate. In addition to its use in the treatment of saline soils, gypsum is sometimes used to add calcium to soil, although it contributes only a small amount, according to the University of Minnesota. Contrary to popular belief, gypsum does not usually affect soil pH, so it shouldn't be used as a liming product. Generally speaking, the best reason to use gypsum as a soil amendment is to remove excess sodium from the soil. It also improves the overall structure of heavy clay soils.

Effects on Soil Salinity

• When gypsum is added to the soil, it allows salt particles to detach from soil particles. Salts tend to stick to soil particles, particularly in arid climates and clay soil conditions. Gypsum replaces sodium particles with calcium particles, which it releases into the soil. A few factors may affect the effectiveness of gypsum in freeing soil salts. Gypsum does not tend to affect layered or heavily compacted soils and it is often effective only in agricultural areas, particularly in the southeastern regions of the United States and in arid or coastal regions.

Other Considerations

• Always obtain a soil analysis before adding gypsum or any other soil amendment to your soil. A soil test will calculate the Sodium Absorption Ratio (SAR) of the soil, which tells you the ratio of sodium particles to calcium and magnesium. This ratio plays a crucial role in the effectiveness of gypsum, according to the Colorado State University Cooperative Extension. Once you have determined whether gypsum is an appropriate soil amendment, apply it carefully and follow manufacturer instructions. Gypsum application is often combined with heavy leaching, which allows sodium particles to leave the soil completely.