Gypsum, a naturally occurring mineral, has been used extensively in agriculture as a soil amendment. It is a source of calcium and sulphur, two essential nutrients for plant growth. But what exactly is gypsum, and how does it benefit the soil? Let’s delve into the science behind gypsum and its role in soil health.

What is Gypsum?

Gypsum, scientifically known as calcium sulphate dihydrate, is a mineral found deposited below the earth’s surface. It is extracted through mining and used in various industries, including construction and agriculture. In agriculture, gypsum serves multiple purposes, including boosting plant nutrition, enhancing soil structure, and reclaiming sodic soil.

Improving Soil Structure with Gypsum

One of the primary benefits of gypsum is its ability to improve soil structure. It promotes soil aggregation, which is the process of joining small clay particles together. This process, known as flocculation, changes the soil composition, making it more conducive for plant growth. It improves drainage, air circulation, root development, and nutrient absorption, especially in heavy clay soils.

Gypsum and Sodic Soils

Gypsum is particularly beneficial for sodic soils, which are characterized by high sodium levels and low calcium levels. The calcium in gypsum, along with proper drainage and tillage, can significantly reduce sodium levels in these soils. Reduced sodium levels improve soil structure, resulting in greater water and root penetration. This process, however, can take years, and small, repeated applications of gypsum are preferred over one large application.

Alleviating Aluminum Toxicity

Another significant benefit of gypsum is its ability to alleviate aluminum toxicity in acidic soils. At a pH lower than 4.5, aluminum in the soil can overpower the ability of hydrogen ions to increase pH, causing toxicity. Gypsum has been shown to be effective at treating this issue.

Gypsum and Soil Fertility

While gypsum offers numerous benefits, it’s important to note that it doesn’t significantly improve soil fertility. It is more soluble than lime and can rapidly add calcium to the soil, which may decrease potassium or magnesium levels. Therefore, it’s crucial to monitor these levels through regular soil testing.


Gypsum is an inexpensive and valuable tool for improving soil structure and promoting healthy plant growth. However, it’s not a one-size-fits-all solution. The amount of gypsum to apply should be determined based on a soil analysis and the specific needs of your soil. Over-application of gypsum can strip essential nutrients from the soil and harm plant growth. Therefore, it’s always best to consult with professionals or conduct a soil analysis before adding gypsum or any other chemical to your landscape.

Gypsum is a beneficial soil amendment that can improve soil structure, promote plant growth, and reclaim sodic soils. However, its use should be based on a thorough understanding of your soil’s specific needs and conditions. Remember, the key to a healthy and productive garden lies in maintaining a balanced and nutrient-rich soil.

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