If your garden is more hard packed clay than pleasantly soft soil, you might be giving up on the idea that you’ll be able to grow much of anything. If this is the case, it’s time to add a special kind of amendment to your soil. One that helps to break up compaction and leaves your plant roots with plenty of room to stretch out and secure themselves.
It’s time to take a look at adding gypsum.
However, gypsum is not universally accepted as a garden amendment. Some people feel strongly that its benefits are vastly overrated and that other supplements are better for your garden than this powdered rock. Though this might be true in some situations, gypsum can certainly help in others.
To clear up any confusion on this controversial additive, read on to learn if it is the right amendment for your garden.
What is Gypsum?
Technically called calcium sulfate, gypsum is a naturally occurring mineral that contains calcium and sulfur. It can be chemically expressed as CaSO42H20.
The word ‘gypsum’ originally comes from the Greek word for ‘plaster.’ Thus, pointing back to the long history of its use as a binding agent, building material and an ingredient in drywall.
The use of gypsum changed 250 years ago once innovative gardeners started to mix it into their less fertile garden lots. When forced to interact with gypsum, fine clay particles begin to clump into larger particles. Thus, making it easier for air, water, and even plant roots to push through. This improves the overall structure of the soil and makes it easier for plants to stay firmly rooted and thrive. However, the soil improving benefits tend to be short term. So, if you find your soil truly depends on it, you’ll need to plan on reapplying every few months.
Where is it sourced from?
One of the best ways to get gypsum is to find a local quarry near you. Of course, they will need to be willing to sell some to you wholesale. The top states where it is mined in the United States are Oklahoma, Iowa, Nevada, California, and Texas.
Because of the controversy over its effectiveness, gypsum can be notoriously difficult to find in garden stores. However, most stores are willing to special order it for you if you request it. In most cases, you can buy it in 50 or 80-pound bags, which should be plenty to start.
Types of Gypsum
There are a few different forms in which gypsum can be purchased for gardens, two of which are listed below.
Powdered Gypsum: Just as the name implies, powdered gypsum is a fine powder that can be easily worked into difficult soil. Therefore, making it a smart choice for new garden beds. Just work it into the soil with a shovel or rake, and allow it to dissolve in water. You can spread out the gypsum through the use of vicon style spreaders that are specifically designed for spreading powders.
Granular Gypsum: With a similar look to lawn fertilizer, granular gypsum is formed into small, uniformly-sized pellets that can be used in any regular fertilizer spreader. This makes it perfect for spreading on existing lawns or gardens where you don’t want to disturb the soil too much. It’s also a good choice in places that get lots of wind that would otherwise blow away all the powder.
How Does It Benefit the Soil and Crops?
Some gardens benefit more from the use of gypsum than others. To find out if your soil will respond well to gypsum, get a soil test to see what the saline levels are. Otherwise, simply observe how much clay is present. Besides clay garden soil, some of the best places to use gypsum are around construction sites where the ground has been compacted through heavy equipment.
Gypsum isn’t known for its fast-acting results, but after consistently adding it to your soil for three years you should notice that your soil is less compacted and more easily penetrated by plant roots. Over time, this soil will better allow water to run through it. Thus, allowing seeds to emerge from the soil faster. This is also a smart strategy for soils in drought areas, as using gypsum ensures that most of the water will make it to the roots of your garden plants, rather than evaporating on the surface.
Another benefit to adding gypsum to your soil is that it can help neutralize acidic soils and reduce aluminum toxicity that usually comes along with it. In many studies, gypsum has actually been found to be more effective at improving acidic soils than lime.
Finally, gypsum can improve the quality of the fruit you grow and even help prevent plant diseases from spreading through your plants. Gypsum tends to be especially helpful for ground growing peanuts that are susceptible to disease, and for preventing blossom end rot from taking out your harvest of watermelon and tomatoes.
Does Gypsum Actually Help?
Looking at the above evidence, it might be hard for you to understand why gypsum has such a controversial reputation for gardeners. The truth is, though gypsum can be exactly what is needed in some garden plots, in most others it makes little impact. Even more so, it can even cause issues with your soil fertility.
It’s no surprise that gypsum is best suited for heavy clay soils. It can work wonders in improving the soil structure of clay soil, but won’t have any effect on variables like soil fertility or pH levels. For this reason, urban soils are rarely improved by the addition of gypsum.
Gypsum naturally reduces salt levels in the soil. This means that it is a smart additive to use in coastal regions that get salt from the breeze. However, it doesn’t work as well in sandy soils and often just adds excess levels of calcium to an area that already had more than enough. Likewise, places that are low in salt might have too much drawn out by gypsum. Thus, the area might quickly become deficient to the point that you need to add more in.
If you think that you have soil that could be benefited by some gypsum, make sure to have a soil analysis performed to reveal information about the levels of mineral deficiency and soil character. Soils that have at least ten percent organic material don’t improve with the addition of gypsum, but if your soil comes up clay filled, it might benefit from some gypsum.
Essentially, adding gypsum to your garden beds probably won’t harm anything. However, it certainly won’t help much either unless you are starting a new garden bed from scratch or have excessively salty soil. The truth is that gypsum is completely unnecessary for the majority of gardens.
General Application Rates
If you decide that your garden will benefit from gypsum, you can plan on applying about 20 pounds for every 100 square feet of garden space. Lawns require much less, about four pounds per 100 feet.
The best time of year to apply gypsum is in the fall. However, the majority of gardeners lay it down in the spring before planting. Gypsum should be added to the garden at least once a year. While also, keeping in mind that it will take several years to build up your soil levels to an amount that will make a big difference.
Additionally, keep in mind that gypsum doesn’t supply many plant nutrients. Thus, a healthy garden will still need a generous dose of organic fertilizer.
Additional Tips for Success
Understanding when to use gypsum in your garden can be confusing. Below are some additional tips to help you out.
- Lime and gypsum provide many of the same benefits for garden plants. Although, lime lowers the acidity of soil by raising the pH levels, while gypsum works by restoring compacted soil. Though excess amounts of lime can burn and damage plants, gypsum has less risk.
- Because drywall is made out of gypsum, some people like to use their excess material in their garden beds as a cheap way to get the benefits of gypsum. This is strongly recommended against, as drywall is made by many different types of companies and tends to be unregulated. Therefore, there is no way for you to know what kinds of chemicals you are introducing into your garden soil.