Gypsum, or Calcium Sulphate, contains about 27.7% Calcium (CaO) and about 40.8% Sulphur (So3).
It is not a new agricultural product; it was used as a fertilizer in Europe in the latter 1800s. We mainly think of it as an ingredient in Plaster board for building, but it also has other industrial and food uses, in addition to its potential to improve soil tilth and health.
Major Benefits of Gypsum
Here are five key (and overlapping) benefits of gypsum.
1. Source of calcium and sulphur for plant nutrition. "Plants are becoming more deficient for sulphur and the soil is not supplying enough it. Gypsum is an excellent source of sulphur for plant nutrition and improving crop yield. Meanwhile, calcium is essential for most nutrients to be absorbed by plants roots. Without adequate calcium, uptake mechanisms would fail, Calcium helps stimulate root growth.
2. Improves acid soils and treats aluminium toxicity. One of gypsum's main advantages is its ability to reduce aluminium toxicity, which often accompanies soil acidity, particularly in subsoil's. Gypsum can improve some acid soils even beyond what lime can do for them, which makes it possible to have deeper rooting with resulting benefits to the crops. Surface-applied gypsum leaches down to the subsoil and results in increased root growth.
3. Improves soil structure. Flocculation, or aggregation, is needed to give favourable soil structure for root growth and air and water movement. Clay dispersion and collapse of structure at the soil-air interface is a major contributor to crust formation. Gypsum has been used for many years to improve aggregation and inhibit or overcome dispersion in sodic soils. Soluble calcium enhances soil aggregation and porosity to improve water infiltration. It's important to manage the calcium status of the soil. In soils having unfavourable calcium-magnesium ratios, gypsum can create a more favourable ratio. Addition of soluble calcium can overcome the dispersion effects of magnesium or sodium ions and help promote flocculation and structure development in dispersed soils.
4. Improves water infiltration. Gypsum also improves the ability of soil to drain and not become waterlogged due to a combination of high sodium, swelling clay and excess water. When gypsum is applied to soil it allows water to move into the soil and allows the crop to grow well.
5. Helps reduce runoff and erosion. Agriculture is considered to be one of the major contributors to water quality, with phosphorus runoff the biggest concern. Gypsum helps to keep phosphorus and other nutrients from leaving farm fields. Gypsum could be considered as a Best Management Practice for reducing soluble P losses.
Using gypsum as a soil amendment is one of the most economical way to cut the non-point run-off pollution of phosphorus."
Applying gypsum is more acceptable as a management practice and more scientists, agronomists and producers are now sharing their results.