Why Use Gypsum: Its Benefits
1. Improves Soil Structure
Gypsum provides calcium, which is needed to flocculate clays in soil. Flocculation is the process in which many individual small clay particles are bound together in fewer but larger particles. This allows root growth and air and water movement.
Gypsum is the most economical way to reclaim sodic soils. The calcium replaces the sodium held on the clay-binding sites. The sodium can then be leached from the soil as sodium sulfate to an appropriate sink. The sulfate is the residue from the gypsum.
Gypsum can prevent crust formation on soil surfaces which result from rain drops or sprinkler irrigation on unstable soil. The gypsum is either surface applied or put in the irrigation system (high grade gypsum). Prevention of crust formation means more seed emergence, more rapid seed emergence, and easily a few days sooner to harvest and market.
Irrigation water from rivers that no longer have sources of leachable salts either penetrates poorly into soil or causes soil particles to degrade, which results in low water penetration. This can be corrected with the use of gypsum.
Soil compaction can be prevented by not plowing or driving machinery on soil when it’s too wet. The compaction in many soils can be decreased with gypsum, especially when combined with deep tillage. Combination with organic amendments also helps, especially in preventing return of the compaction.
Soils that have been treated with gypsum have a wider range of soil moisture levels where it is safe to till without danger of compaction or deflocculation. This is accompanied with greater ease of tillage and more effective seedbed preparation and weed control. Less energy is needed for the tillage.
Gypsum improves water infiltration rates into soils and the hydraulic conductivity of the soil. It is protection against excess water runoff from especially large storms that accompany erosion.
Gypsum immediately decreases the pH of sodic soils and near sodic soils from values often over 9 but usually over 8 to values from 7.5 to 7.8. These values are in the range of acceptability for growth of most crop plants. The level of exchangeable sodium is decreased, which lessens the hydrolysis of clay to form hydroxides. Also, there is release of the acid ions.
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.
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.
Gypsum is a source of calcium which is a major mechanism that binds organic matter to clay in soil. This gives stability to soil aggregates. The value of organic matter is increased when it is applied with gypsum.
Gypsum increases the beneficial effects of water-soluble polymers used as amendments to improve soil structure. Just as with organic matter, the calcium in the gypsum is the mechanism which binds the watersoluble polymers to the clay in soil.
In soils having unfavorable calcium : magnesium ratios, such as serpentine soils, gypsum can create a more favorable ratio.
Gypsum can improve some acid soils even more then lime. Surface crusting can be prevented. The effects of toxic soluble aluminum can be decreased, even in the subsoil where lime will not penetrate. It is then possible to have deeper rooting with resulting benefits to the crops. Gypsum is now being widely used on acid soils.
Gypsum increases water-use efficiency of crops. In times of drought, this is extremely important. Improved water infiltration rates, improved hydraulic conductivity of soil and better water storage in the soil all lead to deeper rooting and better water-use efficiency. 25 to 100 percent more water is available in gypsum-treated soils due to less runoff.
Because it is readily soluble, gypsum results in a proper solute concentration (EC) in soil to maintain it in a flocculated state. It is better environmentally and cost-wise to maintain the needed EC with gypsum than with excess application of fertilizers. Regular annual applications of gypsum are needed for this purpose.
Gypsum is essential when low quality irrigation water must be used. The effective sodium absorption ratio (SAR) of irrigation water should be less than 6 for some crops and less than 9 for others. When it exceeds these limits, gypsum should be applied.
The use of gypsum can decrease wind and water erosion of soil. Severe dust problems can be decreased, especially when combined with the use of water-soluble polymers.
Calcium, which is supplied in gypsum, is essential to the mechanisms by which most plant nutrients are absorbed by roots.
Calcium acts as a regulator of the balance of particularly the micro nutrients, such as iron, zinc, manganese and copper in plants. It also regulates non-essential trace elements. Calcium prevents excess uptake of many of then, and, once they are in the plant, calcium keeps them from having adverse effects when their levels get high.
Gypsum adds to the value of organic amendments. Blends of gypsum and organics increase the value of each other as a soil amendment. Gypsum decreases burn out of soil organic matter when soils are cultivated.
Good fruit quality requires an adequate amount of calcium. Calcium moves very slowly, if at all, and fruits at the end of the transport system get too little. Calcium must be constantly available to the roots. This is especially true in very high pH soils. Gypsum is also known to prevent disease: it is used for peanuts, which develop below ground, to keep them disease free. Gypsum helps prevent blossom-end rot of 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 caused by Phytophthora is partially controlled by gypsum.
Gypsum contains sulfate, a natural form of sulfur which is readily available for soil needs and plant up-take. This replenishes the sulfur which is no longer being added to the soil due to the use of high-analysis fertilizers, which contain very little, if any, sulfur.
A liberal application of gypsum is a good procedure when starting a piece of land into no-till soil management or into pasture crops. Improved soil aggregation and permeability will last for years and surface-applied fertilizers will more easily penetrate into the soil.
Gypsum-treated soil has a lower bulk density compared with untreated soil. Organics can decrease it even more when both are used. The softer soil is easier to till and crops respond better.
Gypsum can improve the response to all other inputs, including fertilizers. It more than adds to their beneficial effects—it multiplies them.
Increased calcium uptake by roots when gypsum is applied can decrease the pH of the rhizosphere adjacent to plant roots. In high pH soils, the added availability of especially iron and zinc is very important to some plant species.
Gypsum can help keep clay particles from adhering to the roots of crops like potatoes, carrots, garlic and beets. This is cost-saving especially at harvest time.
Calcium from gypsum can help decrease volatilization loss of ammonium nitrogen from applications of ammonia, ammonium nitrate, UAN, urea, ammonium sulfate, or any of the ammonium phosphates. Calcium can decrease the effective pH by precipitating carbonates and also prevent ammonia loss to the atmosphere by forming a complex calcium salt with ammonium hydroxide.
Gypsum—for various combinations of the above effects—can substantially increase crop yields. 10 to 50 percent is very common. Gypsum can be a farmer’s friend.