What is gypsum used for in soil

What Is Gypsum: Using Gypsum For Garden Tilth

By: , Certified Urban Agriculturist

Soil compaction can negatively affect percolation, tilth, root growth, moisture retention, and soil composition. Clay soils in commercial agricultural sites are often treated with gypsum to help break up the clay and enhance calcium, which breaks up excess sodium. The effects are short lived but serve to soften the soil enough for plowing and sowing. In the home garden, however, it is not advantageous and regular additions of organic matter are preferred both for cost and side effect reasons.

What is Gypsum?

Gypsum is calcium sulfate, a naturally occurring mineral. It has been touted as beneficial for breaking up compact soil, especially clay soil. It is useful in changing the soil structure of excessively heavy soils which have been impacted by heavy traffic, flooding, overcropping, or simply overly weatherized.

One of the main uses of gypsum is to remove excess sodium from the soil and adding calcium. A soil analysis is helpful in determining if you need to apply gypsum as a soil amendment. Additional benefits are a reduction in crusting, improved water run-off and erosion control, assisting in seedling emergence, more workable soils, and better percolation. However, the effects will only last a couple of months before the soil reverts to its original state.

Now that we have ascertained what gypsum is, it’s natural to question, “Is gypsum good for the soil?” Since it reduces salt levels in soil, it is effective in coastal and arid regions. However, it doesn’t work in sandy soils and it can deposit an excess of calcium in regions where the mineral is already abundant.

Additionally, in areas with low salinity, it pulls out too much sodium, leaving the location deficient in salt. Considering the cost of a few bags of the mineral, using gypsum for garden tilth is uneconomical.

Garden Gypsum Information

As a rule, using gypsum for garden tilth will probably not harm your plants, but it simply is not necessary. Using a little elbow grease and lovely organic goodies from fall clean up or compost worked into the soil to a depth of at least 8 inches (20 cm.) will provide an excellent soil amendment.

Studies have shown that soils with at least 10 percent organic matter don’t benefit from the addition of gypsum. It also has no effect on soil fertility, permanent structure, or pH, while generous amounts of compost will do all that and more.

In short, you can benefit new landscapes by application of gypsum on compacted soil if you have a need for calcium and have salt laden earth. For the majority of gardeners, the mineral is not necessary and should be left for industrial agricultural use.

This article was last updated on 04/19/21

Read more about Soil, Fixes & Fertilizers

While farmers have used gypsum (calcium sulfate dihydrate) for centuries, it has received renewed attention in recent years. This resurgence is due in large part to ongoing research and practical insights from leading experts that highlight the many benefits of gypsum.

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  1. Source of calcium and sulfur for plant nutrition. 

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  2. Improves acid soils and treats aluminum toxicity. 

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  3. Improves soil structure.

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  4. Improves water infiltration.

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  5. Helps reduce runoff and erosion. 

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The latest information on gypsum has been covered in detail at past Midwest Soil Improvement Symposiums. The event — which has been held in conjunction with The Ohio State University’s Conservation Tillage and Technology Conference — typically includes presentations from industry representatives, scientists, consultants, and growers on the use of gypsum to improve soil structure, reduce nutrient runoff, and more.

Here are five key (and overlapping) benefits of gypsum highlighted at past symposiums:

1. Source of calcium and sulfur for plant nutrition. “Plants are becoming more deficient for sulfur and the soil is not supplying enough it,” said Warren Dick, soil scientist and Professor Emeritus, School of Environment and Natural Resources, The Ohio State University. “Gypsum is an excellent source of sulfur for plant nutrition and improving crop yield.”

Meanwhile, calcium is essential for most nutrients to be absorbed by plants roots. “Without adequate calcium, uptake mechanisms would fail,” Dick said. “Calcium helps stimulate root growth.”

2. Improves acid soils and treats aluminum toxicity. One of gypsum’s main advantages is its ability to reduce aluminum toxicity, which often accompanies soil acidity, particularly in subsoils. Gypsum can improve some acid soils even beyond what lime can do for them, which makes it possible to have deeper rooting with resulting benefits to the crops, Dick said. “Surface-applied gypsum leaches down to to the subsoil and results in increased root growth,” he said.

3. Improves soil structure. Flocculation, or aggregation, is needed to give favorable soil structure for root growth and air and water movement, said Jerry Bigham, Professor Emeritus, School of Environment and Natural Resources, The Ohio State University. “Clay dispersion and collapse of structure at the soil-air interface is a major contributor to crust formation,” he said. “Gypsum has been used for many years to improve aggregation and inhibit or overcome dispersion in sodic soils.”

Soluble calcium enhances soil aggregation and porosity to improve water infiltration (see below). “It’s important to manage the calcium status of the soil,” he said. “I would argue it’s every bit as important as managing NPK.”

In soils having unfavorable calcium-magnesium ratios, gypsum can create a more favorable ratio, Bigham added. “Addition of soluble calcium can overcome the dispersion effects of magnesium or sodium ions and help promote flocculation and structure development in dispersed soils,” he said.

“Agricultural soils have been degraded by centuries of farming practices that disturb soils’ physical properties and create imbalances in soil chemistry resulting in compromised soil biology,” adds Ron Chamberlain, an agronomist with GYPSOIL. “As a result, many soils are no longer able to provide enough natural nutrition and adequate root environment for profitable crop growth. By restoring soil physical properties, gypsum facilitates the natural restoration of soil microbiological complexes which in turn improve soil structure and bring balance to soil chemistry.”

4. Improves water infiltration. Gypsum also improves the ability of soil to drain and not become waterlogged due to a combination of high sodium, swelling clay and excess water, Dick said. “When we apply gypsum to soil it allows water to move into the soil and allow the crop to grow well,” he said.

Increased water-use efficiency of crops is extremely important during a drought, added Allen Torbert, research leader at the USDA-ARS National Soil Dynamics Lab, Auburn, AL. “The key to helping crops survive a drought is to capture all the water you can when it does rain,” he said. “Better soil structure allows all the positive benefits of soil-water relations to occur and gypsum helps to create and support good soil structure properties.”

5. Helps reduce runoff and erosion. Agriculture is considered to be one of the major contributors to water quality, with phosphorus runoff the biggest concern. Experts explained how gypsum helps to keep phosphorus and other nutrients from leaving farm fields. “Gypsum should be considered as a Best Management Practice for reducing soluble P losses,” said Torbert, who showed studies on how gypsum interacts with phosphorus.

Darrell Norton, retired soil scientist at the USDA-ARS National Soil Erosion Research Laboratory at Purdue University, added: “Using gypsum as a soil amendment is the most economical way to cut the non-point run-off pollution of phosphorus.”

Editor’s note: This article originally published in April 2013.

31 31 5 The Role Of Gypsum In Agriculture: 5 Key Benefits You Should Know

Matt Hopkins is Senior Online Editor for the Agribusiness Group at Meister Media Worldwide (MMW), including such brands as CropLife, CropLife IRON, AgriBusiness Global, Global Agtech Initiative, and Cotton Grower. He is responsible for managing an array of digital products, including newsletters, websites, video, and social media. Hopkins originally joined MMW in 1994 as an editor for Greenhouse Grower magazine before transitioning to Business Manager of its MeisterPro division. He has a Communications Degree from Cleveland State University. See all author stories here.