Carson Duggar, Agronomy Sales & Seed Specialist
Gypsum has been used as a fertilizer since Benjamin Franklin first applied raw gypsum on his crop fields more than 200 years ago. Today, farmers use gypsum to improve soil tilth, water infiltration and nitrogen uptake, just like Franklin did then. In recent years, it’s had a resurgence with new research highlighting its many benefits.
Gypsum is a mineral naturally found with ground deposits and is most commonly extracted via mining. However, it is also a byproduct of coal-burning electricity plants. This byproduct is good quality, usually containing small, uniform particles which makes it very reactive.
Gypsum works as soil amendment, conditioner and fertilizer. Gypsum is calcium sulfate, and is often confused with lime, or chemically known as calcium carbonate. Considered an excellent source of sulfur and calcium, its chemical formula makes sulfur and calcium more available to plants than other common sources.
Sulfur is essential for the nitrogen-fixing on the nodules of legumes and maximum production. As plants become more sulfur-deficient, the soil alone does not supply enough of it. Research has shown that gypsum can provide sulfur in the soil up to one or two years after the initial application, depending on the application rate.
Meanwhile, calcium is needed for the plant roots to absorb most nutrients. Without calcium, most uptake mechanisms will fail. Gypsum is a moderately-soluble mineral, allowing the calcium to move deeper into the soil than the calcium from lime. Once the plant takes root, calcium promotes rooting depth which can further break up compacted soil and significantly help the uptake of water and nutrients, even during the drier parts of the growing season.
Gypsum also has the ability to improve some acidic soils, particularly in subsoils, by reducing aluminum toxicity on root development with only a slight change in soil pH. This makes it possible for the plant to root deeper, benefiting the overall crop.
It also improves the soil structure, aeration and drainage, which results in increased water infiltration and boost seedling emergence. This is particularly beneficial in a drought, since crops can use water more efficiently. Soils will soak up rainwater faster and deeper, even during heavy rains, which reduces runoff. Gypsum binds phosphorus in the soil, and prevents phosphorus from entering our water system and affecting water quality.
Although it has been in use for over 200 years, gypsum’s added advantages are still being studied by researchers. Currently, using gypsum as a soil amendment is considered one of the most economical methods to reduce the runoff of phosphorus.
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