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Gypsum Applications in Farming: Benefits and Rates

Soil Health · October 2025 · 5 min read

Gypsum (calcium sulfate) is one of the oldest soil amendments in agriculture, valued for its ability to improve clay soil structure without altering pH. It supplies both calcium and sulfur, two essential plant nutrients often overlooked in fertility programs. Understanding when and how to apply gypsum helps you get the most return from this versatile amendment.

What Gypsum Does in Soil

Gypsum is composed of calcium sulfate dihydrate (CaSO4·2H2O), containing roughly 23% calcium and 18% sulfur. Unlike lime, gypsum is pH-neutral and does not raise soil pH. Its primary benefit is clay flocculation, where calcium ions replace sodium on clay particles, causing them to aggregate into larger clumps that improve drainage and reduce compaction.

Gypsum also serves as an excellent sulfur source for crops like alfalfa, canola, and corn that have high sulfur demands. The sulfate form is immediately plant-available, making it a reliable option when soil tests show sulfur deficiency.

Application Rates and Methods

Standard gypsum application rates range from 1 to 2 tons per acre, depending on soil conditions and goals. For general soil improvement on heavy clay, 1 ton per acre is a good starting point. Sodic soils with high sodium levels may require 2 tons or more to achieve meaningful flocculation.

• Surface broadcast is the most common method, using a lime or fertilizer spreader
• Incorporation speeds reaction time but is not required
• FGD gypsum (flue gas desulfurization) is a cost-effective recycled source
• Reapply every 2 to 3 years based on soil test results

When Gypsum Helps Most

Gypsum is most beneficial on heavy clay soils with poor structure, crusting problems, or high sodium levels. It works well on soils that already have an acceptable pH but need structural improvement. Fields with sulfur-deficient soil tests also benefit from gypsum as a nutrient source.

Gypsum is not a substitute for lime when pH correction is needed. Because it does not change pH, it should be used alongside lime, not in place of it. A soil test is the best way to determine whether gypsum will benefit your fields.