Lime and gypsum are common soil amendments, and many homeowners tend to get confused about what each does for turfgrass, and the lawn issues each amendment addresses. Each product can be great for lawns, but neither is always helpful. There are significant differences between them, including what you’re supposed to use each product for. Today, I’m going to clear up all the confusion with a complete lime vs gypsum comparison. I’ll also help you identify signs and symptoms that may tell you your lawn could use an application of lime or gypsum.
Let’s start with the basics for readers who just want a quick answer:
- You should use gypsum when you need to reduce your soil’s salinity (sodium content).
- A lime application is appropriate if your soil’s pH level is too acidic and you want to increase the pH.
The most clear and accurate way to understand if your lawn could benefit from an application of lime, gypsum, or other soil amendments is to pay the $20-30 for a lab-based soil test.
In my experience this is the best way to make the most of your lawn care budget for the season – you spend your money where it’s needed, and don’t waste money on products your yard’s soil doesn’t actually need.
Best Overall Lawn Soil Test Kit
The Soil Test Kit I Use & Recommend
There are many options for testing your lawn’s soil, but I prefer a lab-based soil test that provides a detailed analysis of your soil’s nutrients and what’s needed for your lawn to thrive.
I use this one from MySoil every year.
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I’ve used both Lime and Gypsum on my yard in the past and they’re both really effective. But you’ve got to use them the right way.
I’ll reveal everything you need to know below in today’s detailed lime vs gypsum exploration.
Lime vs Gypsum as Soil Amendments
While there are significant differences between lime and gypsum, one thing they have in common is that they are both soil amendments.
A soil amendment is a substance that you add to your lawn to improve its health and ability to thrive. I’m going to give you the details on lime vs gypsum here.
What is Lime?
You should add lime to your soil when its pH is too acidic. Since lime applications increase the pH of your soil, it effectively sweetens the soil, making it more alkaline.
If you want to understand the nitty-gritty of how soil pH impacts the ability of grass (and other plants) to utilize that expensive fertilizer you’re spreading, you’ll probably love this article on the topic. But basically, if your pH is off, a lot of the fertilizer you spread won’t even be utilized by your turf.
It’s like you’re throwing money away.
Conversely, if your soil is alkaline, you shouldn’t spread any lime, instead your lawn might benefit from an application of Sulphur to nudge the soil pH in the right direction.
You really need to test your soil pH to understand where you’re starting and to learn what you need to apply to correct soil pH.
The Lawn Chick editorial team regularly interviews industry experts to bring our readers the latest science and expert recommendations to complement our own hands-on lawn care experience.
We Asked: How does soil pH impact a lawn’s ability to utilize the fertilizer you apply and the nutrients available in your yard’s soil?
Teri Answered: “Soil pH is a crucial indicator of soil acidity, and tells us if your yard has the ideal pH for the plants (like grass) you’re growing. It also impacts how well grass utilizes applied fertilizer and absorbs soil nutrients. The sweet spot for lawn pH is between 6.5 and 7.0, but most lawns are adaptable, typically ranging from pH 4.0 to 9.0.”
“If your lawn is thriving but the pH isn’t in the ideal range, there’s no need to adjust it. It’s typically difficult to adjust pH levels, but if pH is too high, you can try adding organic matter like compost, and if it’s too low, applying lime can help.”
Natural Science Manager at Sunday
At Sunday, Teri leverages data analysis, lawn and garden industry trends, and customer needs to create impactful content. With a combination of her conservation background and expertise in science communication and content strategy, Teri works to advance sustainable yard care practices on behalf of Sunday.
About the Lime We Apply to Lawns
I usually find lime soil amendments in granular or powder form, but there are pellet products available too. In general, I don’t recommend powder for lawn applications just because it’s messy and difficult to handle.
A few lime products I’ve used with good results and recommend to my readers are:
- Earth Science Lime (one 25-pound bag per 5,000 square feet),
- NutraLime OP Hi-Mag Lime (one 40 pound bag per 5,000 square feet – save 10% with code LAWNCHICK)
- Jonathan Green’s Mag-I-Cal for Lawns in Acidic Soil (one 18 pound bag covers 5,000 square feet / one 54 pound bag covers 15,000 square feet – save 10% with code LAWNCHICK10)
What is Gypsum?
Gypsum is comprised of calcium sulfate dihydrate, and it’s classified as a soft sulfate mineral.
It is a popular soil amendment, especially to use for reducing soil salinity and improving soil structure. A lot of folks claim it helps to break up heavy clay soil, but in my experience you can’t count on that. It’s really best for addressing issues with sodic soil.
Soils with high sodium (salt) levels hold on to water (but don’t release it to your grass). So often sodic soils may appear to be heavy and wet, which confuses some homeowners (they think it isn’t draining well and it must be because the soil is too dense). But for some people, the real issue may be the sodium holding on to that water. Once that issue is resolved, your soil structure will be improved, your lawn will dry out normally, and your grass will be able to access more water.
Most commercial Gypsum for lawns comes in granular form.
For those interested in the science, this video demonstration of the affect gypsum has on sodic soil is a worthwhile watch (and you’ll also learn what “flocculation” means which is a fun word to work into conversation at dinner parties):
Key Differences Between Lime and Gypsum
The main difference between lime and gypsum is simple: they’re made of different things.
As I explained above,
- Lime is made from ground-up limestone rock. It contains calcium carbonate and magnesium carbonate.
- Gypsum, on the other hand, is made from calcium sulfate dihydrate.
There is also a major difference in how and when we should use lime and gypsum on our lawns and in our gardens.
You’ll remember I mentioned that
- we use lime to adjust pH in soil that is too acidic.
- By contrast, gypsum is used for reducing the amount of salt in your soil.
When you use gypsum, you won’t see any meaningful or lasting pH change in your soil, and a lime application won’t address your sodic soil issue in a meaningful way.
Why You Should Use Lime
If your soil is too acidic, you should use lime as a soil amendment. Soil is considered acidic when its pH level is lower than 6.5. A pH level between 6.0 and 7.0 is considered an optimal range for most types of lawn grass.
The farther your soil pH is from this optimal range (in either direction), the less hospitable it will be for your lawn grass. At a pH of 5.5, 33% of the fertilizer you apply to your lawn is wasted, and at 5.0 pH you’re wasting 54% of the fertilizer you throw down.
So it really matters.
Reduce Soil Acidity
Having your soil too acidic can lead to problems for your lawn and garden. When soil is too acidic, you’ll hear other gardeners call it “sour.”
Excessive acidity in soil can cause your soil to be low in minerals, and this will negatively affect soil health.
You can find out your soil’s pH by doing a pH test. Even if you’ve testdoed your soil pH in the past, it might have changed since then.
For example, certain kinds of organic matter, chemical fertilizers, and even heavy rain can make your soil more acidic over time.
In New England, where I live, our soils tend to skew acidic for a few reasons. For instance I have a row of white pine trees in one section of my property, and those needles falling on my lawn and getting incorporated into the soil as they get mulched and decompose makes that part of my lawn more acidic.
I test my soil once a year, and I recommend that you do too. You can get test kits from an extension office near you, or you can find a DIY test like this one from Sunday (save 15% with code LAWNCHICK2024).
How to Use Lime On Your Lawn
I always go with the granular or pelletized lime for my lawn, because I find it to be easy to apply evenly, and it’s not as messy to handle.
You’ll need a good fertilizer spreader or tiller to apply it the right way and get an even application.
Many websites you’ll come across recommend that you spread 50 pounds of lime for every 1,000 square feet of your lawn, but how much you need to apply will vary based on your current soil pH.
Test your soil, follow the manufacturer’s suggested application rate, and then after a few months test your soil again to see if you need a follow-up application.
If possible, split your application up. Do your first lime application in early spring. Do your second one in the fall.
Once you’ve done this, your soil’s pH should be adjusted, and you’ll want to re-test to see where you are.
You’ll have to continue testing the pH level of your soil annually or at least once every two years. Remember, the pH might skew acidic again.
After you dial in your soil pH and reduce its acidity, I recommend an annual application of this product from Jonathan Green. It will gently nudge your soil pH each year without causing a severe swing, and contains valuable humic to improve soil and help your lawn make use of your fertilizer. It’s what I use on my own lawn every year.
Don’t Use Too Much Lime
Like with most soil amendments, you need to make sure that you use the right amount of lime. As I mentioned, there’s a lot of very general and misleading information on the web on this topic.
Don’t go overboard with your lime application. If you use too much lime, your lawn could end up with an iron deficiency.
A lawn with iron deficiency will probably take on a distinctly yellow hue and look unhealthy. You may also notice that the leaf blades have bleach spots.
Why You Should Use Gypsum
You should use a gypsum soil amendment if your soil’s salinity is too high. That means that it contains too much salt (sodium chloride).
If you’re not sure whether your soil has high salinity, do a salinity test (a good lab-based soil test kit will tell you the salt level with accuracy.
You can also use gypsum if you just want to improve your soil’s structure.
The reduction of salt will help water move through the soil the way it’s supposed to, which can make a big difference on the health of your grass and the “feel” of your soil underfoot.
Reduce Salt Content
Excessively high salt content is a problem in soil. It can be toxic to your grass and plants. Your lawn will probably end up dried out and unhealthy.
When there is too much salt in soil, it can drain your plants and grass of the water that it needs.
Excessive salt can stop your plants from growing and thriving as they should. It impedes proper cell development.
If you think your lawn soil might have too much salt, you should get it tested. Contact an extension office in your area, or order one of the at-home lab based soil test kits I’ve recommended in this article.
What salt (salinity) level is right for your soil will vary depending on where you live. Different areas of the country have different normal levels of salt in soil.
Compaction is a big problem with lawn soil. If you let your compaction problem get too bad, your lawn will get very unhealthy and maybe even die.
When soil is compacted, the particles are basically too dense to allow air, water, and nutrients to infiltrate and pass through it. This can starve your lawn of what it needs to thrive.
You’ve probably heard about how you need to aerate your lawn soil if it’s compacted. And that is certainly true. But if your lawn is sodic, using gypsum is also necessary.
Gypsum is effective at easing the density of sodic soils. When your soil is high in salt, each soil molecule is basically coated with sodium, which prevents the molecules from grouping together, blocking exchange sites. You want larger soil particles so that water, air, and nutrients are able to easily pass through the gaps. When gypsum removes the salt coating from soil particles, it can successfully address this problem, loosening your soil.
Improve Water Penetration
As gypsum helps to reduce compaction, it makes your soil better able to absorb water. So, when you irrigate your lawn or when there is rain, the resulting moisture will get down into the ground and reach your grass roots instead of pooling atop your lawn.
Of course, like any other kind of vegetation, grass needs water in order to survive and grow. Find out what species of grass you have to figure out how much moisture it needs each week.
With most turfgrasses, you need to give your lawn between 1 and 1.5 inches of water weekly. When grass doesn’t get enough moisture (for example, because water isn’t penetrating as it should), it will turn brown and eventually die.
Improve Soil Structure
Gypsum is great for helping to reduce soil erosion. It can do this because of how it makes the soil better able to absorb water after it rains, which is key to cutting down on runoff.
When soil is better able to absorb water, that also means that water more quickly and thoroughly gets down through the soil down to the grass roots.
Remember how I mentioned that gypsum also has an aerating effect on soil? Well, that is another reason why this soil amendment helps to improve soil structure.
Helps Neutralize Pet Urine
Some homeowners who struggle to grow grass with dogs have found that sprinkling gypsum on lawns that are the preferred target for Fido’s pet urine can help cut down on the damage. Make sure to water the gypsum in, so that it can drain the excess salts in the urine from your soil.
Signs That Your Lawn Needs Gypsum
You should consider using gypsum if your lawn has compaction, clay soil, or signs it has too much salt.
There are certain signs that you have compacted soil on your lawn. Here are the most common ones:
- Hard to Pierce – Have you tried to pierce the soil with a spade or shovel but it’s too hard? You have compaction.
- No Growth – You may have heavy compaction in areas where you don’t see any vegetation growing.
- Thin Grass – Grass will lack the nutrients it needs in compacted grass, and so it will probably end up thin and unhealthy.
- Water Puddling – As water has difficulty penetrating compacted soil, you may see water puddling on your lawn if you have this problem.
Soil with high clay content (clay soil) is heavy and is prone to compaction. If you’re not sure whether you have clay soil, there are certain characteristics to look out for.
Does your soil feel sticky when it’s wet? When you rub it with your finger, does it look shiny? Both these features are characteristics of clay soil.
Sign of High Soil Salinity
Soil with high salinity (salt content) will probably lead to weak and thin grass and plants. You may even see a white or pale gray layer on the surface of the soil.
Do you live near the ocean? Gypsum is probably your lawn’s best friend.
How to Use Gypsum On Your Lawn?
You will need a spreader to apply gypsum.
Make sure that you apply it evenly, and make sure that you apply the right amount for your lawn size.
For established lawns, you just need to apply to the lawn’s surface, so no need to worry about working it into the soil.
If you’re going to apply gypsum to a garden bed, you should mix some organic matter or compost into it first.
After you’ve put down your gypsum, water your lawn heavily. Plenty of water is necessary to let the gypsum be able to leach the excess salt from your soil.
To get the best results from your gypsum, I recommend aerating your lawn before applying it. You can apply gypsum two or even three times a year, but for many homeowners one application is enough to see results.
Aerate Your Lawn Before Using Gypsum
I always physically aerate my lawn before I put down gypsum, lime or other soil amendments. It isn’t necessary, but I like to include application of these products as part of my big project weekend each fall.
Aerating your lawn puts holes in the soil and breaks up compaction, it also helps get some of the products you’re applying down into the topsoil, which makes it much easier for the gypsum to absorb and be effective.
I like doing core (also known as plug) aeration rather than spike aeration before applying gypsum. A core aerator pulls out plugs of soil, creating small holes for gypsum (as well as water, sunlight, and nutrition) to get through into the soil.
As core aeration is more challenging than many other kinds of aeration, many homeowners like to hire lawn care professionals to get this job done. This is partly because core aeration equipment is costly and heavy, and more challenging to use than other kinds of aerator.
That said, you can rent the equipment you need to DIY the project.
How Much Gypsum Should You Use?
Is your lawn already established? You’ll need about 10 pounds of gypsum for every 150 square feet of your lawn.
But if you have a new lawn, you’ll require about 10 pounds of gypsum for each 100 square feet.
In most cases, however, I recommend homeowners defer to the specific application rate detailed on the bag of gypsum they’ve purchased. Every manufacturer and every product is a little bit different.
When Should You Apply Gypsum?
You should use gypsum on your lawn in the spring and/or fall. These are the best times of the year because there will be enough moisture in the ground for the right effect and conditioning.
Overall, many gardeners say that the fall is the optimal season to put down gypsum. But if you’re like most homeowners using gypsum, you’ll probably apply it in the early spring. If you do this, get your gypsum down before planting grass seed.
If your soil calls for gypsum, I recommend using it a minimum of once a year.
Frequently Asked Questions: Lime vs Gypsum
Even though I’ve covered a lot of information on lime vs gypsum here, you probably still have some questions. That’s why I’ll answer some of the most frequently asked questions below.
How do you know if your lawn needs lime?
If your soil is too acidic, it needs lime. The best way to determine whether your soil is too acidic is to do a soil pH test.
If your soil pH is lower than 6.5, it’s considered acidic. If it’s 5.5 or lower, it’s strongly acidic.
There are some signs of acidic soil that you can watch out for. Some of these include poor grass growth, wilted grass, yellow spots, and even fungal diseases.
Can you put too much lime on your lawn?
Yes, it’s possible to put too much lime on your lawn. Make sure to follow the product instructions that come on the packaging when deciding how much to put down.
If you use too much lime, you could end up making your soil too alkaline. When soil is too alkaline, you can end up with an unhealthy lawn.
For example, your lawn won’t be able to absorb moisture like it should, and it will have trouble getting the nutrients it needs, too.
Where does gypsum come from?
Miners find gypsum in ancient sea-bed sedimentary deposits. There are approximately 19 states where there is gypsum mining in the United States.
The most important states for gypsum mining are California, Texas, Nevada, Iowa, and Oklahoma. When it comes to other countries, Spain, Mexico, and Canada also produce and export gypsum.
Does gypsum raise soil pH?
No, gypsum doesn’t affect soil pH. It’s a common misconception that gypsum will make soil less acidic, as it contains calcium. But that is not the case – it’s typically pH neutral.
If your soil is too acidic, you need to use lime. Lime will increase the pH, making the soil less acidic.
Final Thoughts on Lime and Gypsum for Lawns
So, now you’ve got a pretty good sense of the differences between lime vs gypsum for lawns.
Don’t worry – you’re not alone if you’ve ever gotten mixed up between lime and gypsum, or been unclear about what either product does for soil.
I hope you now have a clear understanding of the differences between these two lawn soil amendments, as well as when and how to use each one.
- You use lime for reducing the acidity in your soil, to raise its pH to a level where your Turfgrass can thrive and utilize nutrients in the soil properly.
- By contrast, we use gypsum for reducing the salinity (salt levels) in soil, as well as improving soil structure. This can help water and nutrients penetrate the soil and reach the roots of your Turfgrass.
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