Regular use of gypsum is essential to the sustainability of most irrigated soils. Irrigated land eventually leads to sodicity and salinity unless extreme care is taken. Gypsum is a key ingredient for the maintenance of agriculture on many types of soils, however it is especially effective at amending clay soils. Advantages of gypsum in addition to prevention and correction of sodicity include greater soil stability of organic matter, more stable soil aggregates, improved water penetration into soil and more rapid seed emergence. The need for gypsum in amounts varying from small to large is almost universal. Gypsum along with water-soluble polymers and nutrients magnify the value of each other. Together they have an important role in making a better environment for growing plants.
Understanding the Different Kinds of Gypsum
When you order “gypsum” do you truly know what you are buying? Ask yourself the following three questions when buying a calcium sulfate product:
Gypsum v. Hemihydrate v. Anhydrite
Gypsum is calcium sulfate dihydrate, which means each molecule of calcium sulfate has two water molecules associated with it. It is expressed as CaSO4 (2) H2O. Wallboard or plaster of paris used commercially has only one-half molecule of water called hemihydrate and another form of calcium sulfate called anhydrite has no water attached. Why does this matter? Calcium sulfate dihydrate or true “gypsum” reacts quickest in the soil as the attached water molecule in the mineral works to drastically increase solubility. Anhydrite or hemihydrate will also provide similar benefits as gypsum, only on a significantly slower time schedule.
Cost per Unit of Calcium Sulfate
Like fertilizers, gypsum is sold in various grades of purity. Although we can blend to any specific purity between 50% and 95%, we inventory set percentage guarantees at 50, 55, 70, 75, 90, and 95%. Because the cost of product increases exponentially the higher the grade, sometimes the best value for the client may be two tons of 50 instead of one ton of 95. We recommend that growers do the the analysis of cost per unit of calcium sulfate delivered and spread using this calculator and consult with your agronomist to make sure you are getting the best bang for your buck.
Origin and Particle Size of Gypsum
Origin and Particle size of gypsum also matters. Generally, the smaller the particle size, the more plant available the mineral. Many gypsum deposits are found in mountain sides, blasted to be removed from other formations and then pulverized to an specific particle size. Others, such as Holloway’s Lost Hills deposit, formed from an ancient calcium rich lake bed that evaporated over millions of years. Read the benefit of the origin of such product here.