How much gypsum to add to soil

Apply Gypsum for Clay Soil

If you are applying gypsum to protect against exposure to de-icing salts, apply 1/2 pound of gypsum per square foot of soil, advises the University of Maryland Extension. Gypsum is not effective and may damage plants if your soil pH is 5.0 or lower.

Adding gypsum to your soil might result in a deficiency of iron and magnesium, as gypsum tends to add to the leaching of these minerals from the soil. Adding gypsum to your lawn may harm beneficial mycorrhiza around tree seedlings’ roots, which could threaten the trees’ survival.

Add powdered gypsum at the rate of two to three handfuls per square metre, then dig the soil over and water it in. (It will take several months to get the full effect. However, for a quicker option, for example, in planting holes, use a liquid clay breaker with organic matter*.

To use gypsum as a soil amendment, spread it over soil at a rate of about 10 to 15 pounds per 100 square feet of soil surface using a garden spreader or by gloved hand, then till it into the top 6 to 8 inches of soil. Handle gypsum carefully and apply according to manufacturer recommendations.

After about three years the soil will be in much better shape and any crops growing in it will be healthier and more bountiful. Powdered gypsum does take a fairly long time to have any real meaningful effect though. It takes several months, and in extreme cases several years, for powdered gypsum to do its work.

Gypsum neutralizes the mineral salts in pet urine, resolving odors and preventing lawn damage. Gypsum may be applied any time of year and, depending on the needs of your particular lawn, we may apply it two to three times a year.

Application strategies

Depending on conditions, the typical application rates for gypsum range from 500 to 4,000 pounds per acre, Chamberlain pointed out. He recommended the higher rates for soil amendment and the lower ones for crop nutrients.

Add gypsum (calcium sulfate – one cup per plant or one to two pounds per 100 square feet) to the soil before planting. Gypsum works more quickly than lime to supply calcium to the plant.

The gypsum requirement factor is calculated as follows, using a soil bulk density of 1.34 g/c.c. 100 m × 100 m × 0.30 m or 10,000 cm × 10,000 cm × 30 cm = 3 × 10⁹ c.c. Therefore, the weight of soil per hectare. = 40,20,000 kg of soil per hectare 30 cm.

Gypsum (CaSO4 • 2H2O) contains 17-20% calcium and 13-16% sulfur. This equates to roughly 400 pounds of calcium and 320 pounds of sulfate-sulfur for a typical application rate of 1 ton per acre, according to Ron Chamberlain, chief agronomist for GYPSOIL/BRM, a Chicago-based company that markets GYPSOIL brand gypsum.

Gypsum helps soil better absorb water and reduces erosion. It also cuts down on phosphorus movement from soils to lakes and streams and improves the quality of various fruits and vegetables, among other benefits.”

Gypsum is NOT lime.

In order to adjust soil pH, liming products must contain carbonate (CO3-) which reacts with hydrogen ions to neutralize soil acidity. Gypsum is calcium sulfate (CaSO4). While the calcium will displace hydrogen ions, these ions will remain in solution and will not adjust soil pH.

Gypsum (calcium sulfate) or lime can be used to help leach salt from the soil. The calcium in these products replaces the sodium salt from the soil exchange sites and helps bring the salt into solution. Large concentrations of salt may be leached from a soil in this way.

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO ₄·2H₂O. It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard/sidewalk chalk, and drywall.

Put some soil in clean water and shake it until it goes milky. Then stand it for about five or 10 minutes. If it doesn’t clear in the water, chances are it is going to respond to gypsum.

Gypsum therefore improves soil conditions much more rapidly than lime and will affect soil conditions to a greater depth than lime will. Gypsum will supply calcium to deeper depths than lime. This will improve subsoil conditions, and allow for greater root growth (better nutrient and water efficiency).

Lime vs gypsum

Lime is a carbonate, oxide or hydroxide of calcium. It is used to increase soil pH and provide calcium ions in the soil. Gypsum is calcium sulphate. It is also used to provide calcium ions in the soil, but does not have the effect of increasing soil pH.