Calcium Sulfate Dihydrate is the most popular and most commonly used material to reclaim sodic soils and treat soils irrigated with reclaimed, sodic water. Please note that this article started with calcium sulfate dihydrate as the source, not calcium sulfate. I want to be clear, there is a huge difference; knowing what you’re applying is key to reclaiming your golf course.
Calcium sulfate dihydrate is a form of gypsum that has 2 molecules of water attached to the crystalline structure of the gypsum, where calcium sulfate has NO water molecules attached. This is vitally important because the molecules of water aid in the solubility of the material. Gypsum is just like any other fertilizer when it comes to providing nutrients, it has to solubilize in order to provide nutrients.
High sodic soils and poor quality irrigation water are most commonly found in the southwestern states but depending on the water source, it can be found in other regions of the country. Using a gypsum source that is high in purity, finely ground and then pelletized for precision applications will be your best opportunity to reclaim your turf.
Soil salinity is the salt content in the soil and salts are the soluble nutrient ions in the soil solution. These salts can accumulate in the soil from multiple sources. They can originate from natural weathering of minerals that form the soils, they can accumulate in arid climates with little to no rainfall or from your irrigation source. Evaporation can also bring salty water to the surface, leaving minerals behind.
Sodic soils have very poor structure and tend to develop poor drainage over time because the sodium ions on the clay particles cause the soil particles to disperse. Typically, this results in soils that are hard and crusted-over when dry with poor water infiltration. This can lead to shallow rooting, decreased germination rates, and overall poor stands of turf.
The soil can only be reclaimed by removing the sodium from the root zone by applying calcium sulfate dihydrate to displace the sodium ions and enough clean (if possible) water to flush the sodium from the root zone. Gypsum plays a key role in improving the soil structure by replacing the sodium with calcium that will improve water infiltration.