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How to Use Gypsum As a Soil Amendment

Updated: Jan 28, 2023


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Soil plays a crucial role in plant growth by supplying them with nutrients and water and anchoring their roots firmly. Continuous tilling, chemical fertilizers, wind and flood erosion, and poor drainage leads to low fertility and high accumulation of toxic substances in the soil. This, in turn, lowers its productivity.


Soil amendment involves enriching it by applying various substances to modify its physical properties. For example, grass clippings preserve moisture, compost manure enhances fertility, while wood ash raises its pH.


For about three centuries, farmers and gardeners have applied gypsum to their yards improve soil properties. Before adding gypsum powder to your kitchen garden, farm, or your new lawn, you have more to learn about gypsum as a soil amendment. Read on and learn more from this post.


What is Gypsum, and How Does It Alter Soil Properties?


Gypsum one of the common normal salts, is found within the earth. It is a sedimentary rock in different colors, including white, purple, black, and pink. The different shades are caused by the impurities present in the rocks. Its chemical name is hydrated calcium sulfate. When packaged, this salt exists in powder or granular form.


Gardeners use gypsum as soil amendment because it modifies its properties in the following ways:


Supplies essential plant nutrients. Calcium sulfate contains calcium and sulfur, which are crucial to plant growth. Calcium helps in root and stem formation, while sulfur aids chlorophyll formation.


Lowers aluminum ions concentration. Calcium is more reactive than aluminum, and therefore calcium ions from the salt displace aluminum ions in the soil. This reduces the aluminum toxicity making it more alkaline.


It improves aggregation by supplying calcium which binds its particles and organic matter through flocculation.


Lowers sodium concentration in sodic soils by decreasing the sodium exchange percentage.


How Do You Apply Gypsum?


Hydrated calcium sulphate application offers an excellent way of improving the soil texture and other properties. However, it is not ideal for all garden types.

Caution: Before applying the salt to your lawn or yard, conduct a soil pH test on samples collected from different parts of your lawn. If you obtain a pH below 5, gypsum is not the best soil amendment for your garden.

If you obtain a pH greater than 5, the garden is alkaline. Hydrated calcium sulphate works best here, therefore, you can apply it sparingly in the following steps:


1. Work out the area of your garden. Knowing the size of your garden is important to help you apply the right amount of calcium sulfate. Too much calcium sulfate application on your lawn can affect it adversely through the over-tilled garden effect. This may lead to loss of nutrients and erosion.


The right amount of calcium sulfate applied per square foot is about 0.3 kilograms.


2. Use a lawn spreader to apply gypsum evenly to your garden while walking back and forth until you cover the entire area.


3. Reapply after one year, ensuring you test for the soil acidity first.


It takes time for gypsum to make a remarkable improvement in your garden, therefore, you need patience and consistency in applying it annually.


How Much Gypsum Should I Add To the Soil?


The amount of gypsum you apply depends on many factors, such as:


The soil type in your garden: Clay responds better to gypsum amendment because of its tiny particles, which are easily aggregated by calcium. If you are doing soil amendment for a lawn, gypsum is ideal because the earth material around construction sites is compact from the heavy machinery and equipment used.


The soil pH: Calcium sulfate works better at high pH and high sodium ion concentration.


The crops you grow: Ground-growing crops such as peanuts and tomatoes thrive in gypsum-treated soil because it prevents blossom end rot.


Tip: The ideal amount of hydrated calcium sulfate for 100 square feet is about 5kg and should be applied evenly. Lawns require less since they are rich in composite from grass clippings.

When Should I Apply Gypsum?


You can apply gypsum to your lawn or garden at any time of the year. However, there are seasons when the gypsum amendment is more necessary. For example, during winter, salts from weathering rocks and sodium chloride used in defrosting roads accumulate in the soil.

Tip: It is advisable to apply gypsum after winter to dislodge the salt ions and water your soil to leach them away.

When you aerate your lawn, the aerator creates spaces in the soil ideal for gypsum powder penetration. This should precede watering the yard to aid calcium sulfate in leaching excess sodium and aluminum ions.


How Long Does Gypsum Take To Work?


Applying gypsum for soil amendment works in different time lengths ranging from seven days to three years. For example, it takes less than a week for calcium sulfate to dissociate to calcium and sulfur, which are essential nutrients for plant growth. If you apply gypsum on your lawn today, your grass will grow healthier within a week from the additional nutrients.


Some properties, however, take longer to change after application. To lower sodium and aluminum concentration, for example, requires a lot of water. If you depend on rainwater, it may take longer to leach away the minerals. However, you can water the garden to quicken the process.


Earthy matter and organic particle aggregation is a gradual process. It requires three or more applications to achieve your desired outcome. Furthermore, the soil gets exposed to depletion by human activities, and restoring it requires consistent amendment.


Tip: Whatever time of the year you apply calcium sulfate dihydrate to your garden, you need to reapply at the same time for 3-4 consecutive years.

Final Thoughts: Is Gypsum Effective In Soil Amendment?


Gypsum application is an effective way to modify your garden and boost its productivity. Being neutral, this salt does not alter the soil pH like other compounds such as plant growth boosters and herbicides. Furthermore, it exists naturally as gypsum rock and is therefore affordable and harmless to humans and animals.


However, don’t be fooled that gypsum can work miracles in your garden without extensive soil analysis. You need to test the soil acidity and determine if it requires gypsum treatment.


Other methods of restoring soil fertility include composite manure application, mulching, and preventing erosion.










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