Gypsum helps prevent blossom-end root of watermelon and tomatoes and bitter pit in apples. Gypsum is preferred over lime for potatoes grown in acid soils so that scab may be controlled. Root rot of avocado trees caused by Phytophthora is partially controlled by gypsum. A liberal application of gypsum is a good procedure for starting a piece of land into no-till soil management or pasture. Improved soil aggregation and permeability will persist for years and surface-applied fertilizers will more easily penetrate as result of the gypsum.
Organics can even decrease it more when both are used.
Gypsum Decreases the Toxic Effect of NaCl Salinity Calcium from gypsum has a physiological role in inhibiting the uptake of Na by plants. For species of plants not tolerant to NA, Ca protects from toxicity of NA but not Cl. Calcium can decrease the effective pH by precipitating carbonates and also by forming a complex calcium salt with ammonium hydroxide which prevents ammonia loss to the atmosphere. Actually calcium improves the uptake of nitrogen by plant roots especially when the plants are young. Root Crops Gypsum can help keep clay particles from adhering to roots, bulbs and tubers of crops like potato, carrots, garlic and beets.