Farmer’s best friend - Almost 40 benefits from its use on land have been documented.

Regular use of gypsum is essential to the sustainability of most irrigated soils. It has been used as a soil amendment and fertilizer for over 200 years.

Gypsum is calcium sulfate. The most common form of it is the dihydrate which means that each molecule of calcium sulfate has two water molecules associated with it. 

The plaster of Paris used commercially has only one-half water and another form called gypsum anhydrite has no water. Much of the gypsum used in agriculture is mined and then pulverized to desirable particle sizes. Gypsum is also a by-product of various manufacturing operations. For many reasons, gypsum can be a farmer’s best friend. 

Almost 40 benefits from its use on land have been documented.

Some reasons are multiple and interrelated.

pink gypsum helps soil structure, adjust soil chemistry, increase water efficiency
pink gypsum helps with the yield on Almond farms

1. Gypsum Improves Soil Structure.

Gypsum provides calcium which is needed to flocculate clays in acid and alkaline soil. It is the process in which many individual small clay particles are bound together to give much fewer but larger particles. Such flocculation is needed to give favorable soil structure for root growth and air and water movement.

2. Gypsum Prevents Crusting of Soil and Aids Seed Emergence.

Gypsum can decrease and prevent the crust formation on soil surfaces which result from rain drops or from sprinkler irrigation on unstable soil. It can even prevent crusting that results when acid soils are limed, the gypsum is coapplied with the lime. The gypsum is either surface applied or put on in the irrigation system. Prevention of crust formation means more seed emergence, more rapid seed emergence, and easily a few days sooner to harvest and market. Seed emergence has been increased often by 50 to 100 percent. The prevention of crusting is dispersive soils is a flocculation reaction.

3. Gypsum Improves Low-Solute Irrigation Water

Gypsum is used to increase the solute concentration of low-solute water used for irrigation. Irrigation water from rivers that no longer have sources of leachable salts wither penetrates poorly into soil or causes soil particles to degrade which results in lower-water penetration. Rainwater can behave the same way and result in soil compaction. The problem can be corrected with surface-applied gypsum or application to the irrigation water.

4. Gypsum Increases the pH of Acidic Soils

One mechanism in which gypsum can increase soil pH enough in some acid soils to sufficiently decrease the level of soluble aluminum to grow crops satisfactorily is replacement of hydroxyl ions from some clay lattices by sulfate ions.

5. Gypsum Improves Swelling Clays

Gypsum can decrease the swelling and cracking associated with high levels of exchangeable sodium on the montmorillonite-type clays. As sodium is replaced by calcium on these clays, they swell less and therefore do not easily clog the pore spaces through which air, water and roots move.

6. Gypsum Prevents Waterlogging of Soil

Gypsum improves the ability of soil to drain and not become waterlogged due to a combination of high sodium, swelling clay, and excess water. Improvements of infiltration rate and hydraulic conductivity with use of gypsum add to the ability of soils to have adequate drainage.

7. Gypsum Makes Excess Magnesium Non-Toxic

In soils having unfavorable calcium; magnesium ratios, such as serpentine soils, gypsum can create a more favorable ratio.

8. Gypsum Corrects Subsoil Acidity

Gypsum can improve some acid soils even beyond what lime can do for them. Surface crusting can be prevented. The effects of toxic soluble aluminum can be decreased, including in the subsoil where lime will not penetrate. It is then possible to have deeper rooting with resulting benefits to the crops. The mechanism is more than replacement of acidic hydrogen ions which can be leached from the soil to give higher pH. Hydrogen ions do not migrate rapidly in soils containing clay. It is suggested that the sulfate from gypsum forms a complex with aluminum which renders the aluminum non-toxic. Also suggested is that the sulfate ions react with iron hydroxide to release hydroxyl ions which give a lime effect to increase soil pH. Gypsum is now being widely used on acid soils.

9. Gypsum Improves Water-Use Efficiency

Gypsum increases water-use efficiency of crops. In areas and times of drought, this is extremely important. Improved water infiltration rates, improved hydraulic conductivity of soil, better water storage in the soil all lead to deeper rooting and better water-use efficiency. From 25 to 100 percent more water is available in gypsum treated soils than in non-treated soils.

10. Gypsum Helps Plants Absorb Plant Nutrients

Calcium, which is supplied in gypsum, is essential to the biochemical mechanisms by which most plant nutrients are absorbed by roots. Without adequate calcium, uptake mechanisms would fail

11. Gypsum Increases Value of Organics

Gypsum adds to the value of organic amendments. Blends of gypsum and organics increase the value of the other as soil amendments, especially for improvement of soil structure. High levels of soil organic matter are always associated with liberal amounts of calcium decreases burn out of soil organic matter when soils are cultivated by bridging the organic matter to clay.

12. Gypsum Improves Fruit Quality and Prevents Some Plant Diseases

Calcium is nearly always only marginally sufficient and often deficient in developing fruits. Good fruit quality requires an adequate amount of calcium. Calcium moves very slowly, if at all, from one plant part to another and fruits at the end of the transport system get too little. Calcium must be constantly available to the roots. In high pH soils, calcium is not available enough; therefore, gypsum helps. Gypsum is used for peanuts, which develop below ground, to keep them disease free. Gypsum helps prevent blossom-end root of watermelon and tomatoes and bitter pit in apples. Gypsum is preferred over lime for potatoes grown in acid soils so that scab may be controlled. Root rot of avocado trees cause by Phytophthora is partially corrected by gypsum and organics. Gypsum is a source of fertilizer sulfur. Due to the trend to production of high-analysis fertilizers and due to the need of removing sulfur dioxide emissions in industrial operations to give cleaner air, and more and more sulfur deficiencies are present in agriculture.

In Summary

Regular use of gypsum is essential to sustainability of most irrigated soils. Gypsum is a key ingredient for the maintenance of agriculture on many types of soils. Controlling pH levels is the key factor in the success of your soil. The pH is important because it influences the availability of essential nutrients. Getting a proper diagnostic on your soil allows agronomists to recommend custom blend of soil amendments that will help your particular soil thrive.