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Gypsum is an excellent source of sulfur and calcium, and many organic gardeners apply this amendment as a treatment for compacted soil. It improves the soil’s physical properties.
For instance, it helps with soil aggregation, which is a phenomenon that determines the arrangement of soil particles.
Better aggregation indicates better aeration, water retention capacity, less compaction, and better stability.
Even if you want to treat the hard clay soils of your garden, gypsum can be a great choice. It also reduces the leaching loss of phosphorus.
In a nutshell, you will get multiple benefits by applying this amendment to your garden. This article will explain the nuts and bolts of using gypsum in gardening.
What is Gypsum Fertilizer?
Gypsum is a natural mineral that is chemically known as calcium sulfate dihydrate. It means that gypsum contains one molecule of calcium sulfate and two water molecules.
This product has been used for a long time to improve the overall structure of the soil.
The most amazing fact about this naturally occurring mineral is that when Ca2+ is released in the soil solution, it replaces the Na+ from exchangeable sites.
As a result, Na+ is lost from the soil by leaching. Therefore, if your garden soil has too much sodium content, you can apply this soil amendment.
There are two significant types of gypsum that a gardener can purchase:
Powdered gypsum
The powder form of gypsum is good for creating new garden beds. It would be best to mix the powder with the topsoil with a rake or shovel to make it more effective.
Granular gypsum
These are uniformly-sized, small pellets. You can apply it to the existing gardens and lawns. Even if your garden receives strong winds, you can use this form of gypsum as a soil amendment.
Why Use Gypsum in Gardening?
Gypsum fertilizer can be advantageous in multiple ways. We will mention some of the benefits that a gardener can get after applying gypsum.
Good Source of Essential Nutrients
Gypsum is a source of essential nutrients, like calcium and sulfur. Sulfur remains in the soil as a sulfate ion, susceptible to leaching loss.
This is why we should provide additional sulfur by adding gypsum. Also, without the presence of sufficient calcium ions, uptake mechanisms fail.
Eliminates Mineral Toxicity in the Soil
Gypsum can eliminate aluminum (AI) toxicity, which is detrimental to plants [1]. When soil pH reduces or soil acidity increases, aluminum is released from the soil minerals and comes into the soil solution.
Ca2+ ions replace Al3+ from the exchangeable sites, and Al3+ forms aluminum sulfate or aluminum-hydroxyl-sulfate which is less toxic [2]. Thus Ca2+ ions reduce aluminum toxicity.
Improves Soil Structure
Gypsum improves soil structure, one of the most critical soil physical characteristics, by adding Ca2+. Calcium ions improve soil structure because they act as cementing agents between the particles. Hence, particles can easily get attached and create soil aggregates.
Better soil structure means better aeration capacity, favorable root growth, nutrient absorption, ideal soil temperature, and a better soil hydrological cycle.
Increase Water Infiltration
This amendment increases the water infiltration rate and reduces surface runoff and erosion if your garden soil is rich in sodium.
In heavy clay soils, gypsum promotes better aggregation, which increases the total porosity of the soil.
Higher porosity indicates a better water infiltration rate, which reduces surface runoff or overflow. As a result, there will be less erosion in your garden.
Increases Phosphorus in Acidic Soil
Gypsum can increase the availability of phosphorus in acid soil. Phosphorus is a double-critical element because it is highly mobile and becomes unavailable when the pH levels fluctuate significantly.
For example, phosphorus reacts with aluminum or iron at a pH level of less than six and forms unavailable compounds.
On the other hand, at a pH level lower than 7, it reacts with calcium and precipitates as a calcium-phosphate compound.
Limitations of Using Gypsum in Gardening
- Gypsum is ineffective at increasing water infiltration if your garden soil doesn’t have any problems regarding sodium content. Also, if the pH level is less than 5, applying gypsum will reduce plant growth.
- It can not improve the overall soil fertility status.
- There is a higher chance that Ca2+ ions will replace magnesium and potassium ions from the exchangeable sites. So, you must apply it after conducting a soil test.
- High calcium levels will make the phosphorus unavailable because calcium will react with the phosphorus and make it inaccessible.
- It may not improve the structure of sandy soils.
How Much Gypsum to Apply in Gardening?
Before you apply gypsum to the garden, make sure that you do a soil analysis to know the status of your soil nutrients.
If you live in coastal or arid regions, you have to do it because these regions have high sodium levels and swelling clay problems.
For highly acidic soils, you should apply lime before adding gypsum. Dolomite lime in this condition is the best choice.
While using these amendments, make sure to apply them a few months before the growing season.
For the existing lawns, you can use a lawn spreader at 40 lbs per thousand square feet, and for the heavy clay soil, you should use a broadcast spreader at a rate of 2.5 to 5 tons per hectare.
FAQ
Is gypsum good for the soil?
Yes, gypsum is good for gardening soil. The purpose of gypsum is to lower the salinity content of the soil. It is very effective in coastal and arid regions where salinity levels in the soil are high. Gypsum helps the soil absorb water more effectively and it also helps to decrease erosion. In addition, it decreases the amount of phosphorus which in turn raises the quality of a variety of fruits and vegetables.
What is gypsum used for in gardening?
Gypsum in gardening is mainly used for reducing compaction, sodicity, and aluminum toxicity problems. One way that gypsum can help release clay soils and improve soil structure is by turning small, tightly packed particles into larger clusters. This makes the soil more permeable and makes it easier for air, water, and nutrients to get into the soil.
Can you apply gypsum and fertilizer together?
Yes, you can mix fine powdered gypsum with compost to apply in the garden. In today’s fertilizer, the components, such as urea, sulfate, and phosphates, can be combined with gypsum.
Does gypsum reduce or increase salt levels in soil?
Gypsum increases the salinity in the soil. Gypsum becomes soluble and, as a result, the extra salt is leached into the soil increasing the level of salt content. (increases salinity). The science behind this is that the formation of gypsum, which contains calcium, can cause a rise in salinity because it removes sodium from the exchange complex. This, in turn, gypsum makes soil saltier.
Does gypsum reduce soil acidity?
Gypsum will not lower the pH of the soil; in fact, it rarely changes soil pH. There is no change in the soil’s pH as a direct result of the gypsum itself because the calcium in the gypsum will displace the hydrogen, but the hydrogen will still be present in the soil solution. When the pH of the subsoil is slightly acidic, aluminum becomes more water-soluble and will start to harm the plant’s roots.
Other Soil Amendments
Besides gypsum, there are other types of soil amendments to consider using. Each one has its own purposes, such as perlite to increase water drainage or coconut coir for moisture retention.
Below is a short list of soil amendments to use in gardening.
Perlite: Perlite is a lightweight, porous volcanic rock that is often used in gardening as a soil amendment. It helps improve the aeration of the soil, making it an effective tool to improve water drainage and improve plant growth.
Vermiculite: This soil additive is beneficial to soil because it aerates the soil while at the same time retaining water and nutrients, which are then gradually released. Because of this, vermiculite can be useful for both planting seeds and propagating plants. Adding it to the soil for indoor plants can be beneficial.
Coconut coir: Also known as coco coir or coco peat, it is a natural soil amendment made from coconut husks. Coconut coir is also known as coco coir or coco peat. It is high in nitrogen, phosphorus, potassium, and magnesium. Also, coconut coir is a low-impact material that can replace peat moss in potting soils. It helps retain and drain water. The main purpose of adding coco peat to potting soil is to improve drainage and water retention. One problem with coco coir is that it doesn’t have much in the way of nutrients.
Compost: Compost consists of organic material that has been decomposed by microorganisms. Compost also improves the soil’s ability to retain water while increasing the soil’s availability of organic carbon and nutrients. In addition to improving the environment in your garden, compost also helps to reduce landfill waste. It is one of the most effective organic fertilizers for any soil type.
Conclusion
Gypsum provides two essential nutrients to crops and is an excellent treatment for soil compaction.
Remember that soil composition will take years to change, and larger gypsum particles may take even more time. Therefore, you can not expect the results so quickly.
Although gypsum is advantageous in multiple ways, there are drawbacks. Hence, we recommend mixing other organic fertilizers with gypsum and applying them.
Lastly, if you are treating acid soil, you must use lime, not gypsum.
References
Lindsey Hyland grew up in Arizona where she studied at the University of Arizona’s Controlled Environment Agriculture Center. She continued her gardening education by working on organic farms in both rural and urban settings. She started UrbanOrganicYield.com to share gardening tips and tactics. She’s happy to talk about succulents and houseplants or vegetables and herbs – or just about anything in a backyard garden or hydroponics garden.