Lawns are meant to be green, lush swathes of thriving turf. Yellow or brown is just not tolerable.
There’s a bewildering array of reasons why a lawn might start to yellow, but one of the most common is acid soils. It’s thankfully easy to diagnose and treat – provided you know how.
I’m going to run you through some of the basics of how to spot when your lawn needs lime, how much, and how to go about it. Let’s get started!
Table of Contents
What is Liming?
Liming is the process of applying crushed or ground limestone over your lawn.
Chemically it’s mostly pure calcium carbonate or something similar, with many commercial products containing magnesium carbonate, calcium sulfate, or a similar calcium carbonate equivalent.
As it dissolves, the minerals contained in the limestone react with the soil, reducing its acidity.
Most plants need the soil around them to sit at a relatively neutral pH – somewhere between 6.0 and 7.0.
If your soil slips out of that pH range, it changes the availability of nutrients in the soil, binding them into the ground. It becomes difficult for your plants to nourish themselves, resulting in chlorosis – yellowing leaves.
How Often Should You Put Lime On Your Lawn?
You should apply lime to your lawn when the soil pH falls below 6.6.
Depending on your location, soil makeup, grass type, and environmental conditions, this could be anywhere between once a year and once every 3 years.
The best way to decide when to lime your lawn is by conducting a soil test every year. After the first couple of years, you will have a good idea about the liming schedule you’ll need moving forward.
How To Tell If Your Lawn Needs Lime
Despite what farm lore and old wives’ tales may have to say, the only way to tell if your lawn needs a dose of garden lime is to perform a soil test.
While acidic soil is often a cause of yellow grass, iron deficiency brought on by alkaline soils will have the same impact – and adding any liming materials to alkaline soil will damage the lawn grasses even more.
A home soil pH test kit is simple to use and will give you the lawn’s pH range. Many soil test kits also check for essential nutrients, and very fancy ones will also check the levels of micronutrients, too. They’re easy to find at your local garden center and are widely available online.
If you want, you can also enlist a professional test service. If you’re in the United States, many Agricultural Extension Services provide low-cost soil testing services.
They’ll also guide you through the soil test results and provide advice that suits your local conditions, like recommending the best time of the year to apply your lime products and how to treat your particular type of grass.
Some grasses like bentgrasses and fine leaf fescues will grow fine in acid soil around pH 5.0. It really is worth taking a bit of professional advice before you start throwing around bags of chemicals.
That said, there are definitely warning signs that will tell you it’s time to test. These include
- Sudden proliferation of clover, moss, or other common lawn weeds. Weeds are generally acid-loving plants. Dormant seeds will sprout when acidic conditions develop.
- An increase in lawn pests. While insect pests don’t care a jot for the state of the soil, they do love sick or ailing plants. If your beautiful lawn loses its vigor, insect pests will move right on in.
- Yellowing or browning areas of turf. If your soil’s pH level slips out of that ideal pH range of 6.0 and 7.0, the availability of nutrients drops. No amount of fertilizer will help if it’s all chemically bonded into the soil. You still need to test, however – alkaline soil also causes even discoloration across what should be a lovely green lawn.
- Fluctuating weather conditions can also contribute to changes in your soil pH. Consistently wet weather with too much rain leeches the soil of minerals that impact the pH, and during dry weather, your grass uses different ratios of those important nutrients that it draws from the soil, changing the chemistry in the process.
- Soil type and composition play their part, too. Heavy clay soil without much organic matter will need more lime before the pH shifts than light sandy soil or one that’s been mulched for years. Coastal soils also tend to have a lot of marine salts in them, resulting in a lower pH.
How To Test Soil pH Levels
The easiest of all soil test kits uses pH strips ‘or an indicator solution to determine the soil’s pH level. They come complete with instructions and are generally very easy to use.
The process typically involves taking soil samples, dissolving them in water, and then measuring the pH of the resulting muddy solution. Each kit will have its own procedure, so it pays to read the instructions.
One thing they have in common, however, is that they generally ask you to take more than one soil sample.
The pH of the soil will change depending on what’s happening nearby – your lawn care practices, the presence of other plants, runoff from garden beds, and the like. For best results, you’ll need to keep those samples separate.
You may find that you have the right soil for healthy growth across most of your lawn and that only a small application of lime is required to get the soil’s pH levels back in line.
How to Apply Lime to Lawns
Like any soil amendment, it’s important to use the best tool for the job, both for safety reasons and overall ease of application.
Lawns play host to children, pets, picnics, and barbeques, and any chemical strong enough to shift soil acidity must be used responsibly.
What You Need for Lime Application
There are a few types of lime to choose from. Most are calcitic lime derived from limestone, but other options are also available. Each has its own properties, so always read the instructions thoroughly before use.
The most common forms found in garden centers are:
This lime is made by grinding limestone into a fine powder and then forming the powder into small pellets. The lime pellets are easy to handle and apply and can be spread with a fertilizer spreader.
This type of lime is made by grinding limestone into powder form. It’s sometimes called ‘powder lime’ and is particularly good at working past dense grass blades down to where it’s needed.
Agricultural lime is specifically formulated to be used on farmlands. It is finely ground and tends to pack a punch. The texture is great for uniform coverage.
This lime is made from dolomite rock and contains calcium and magnesium. It is suitable for acidic soils that are low in magnesium, so you can correct an acidic pH and some of the nutritional drama they cause at the same time.
Potted Exotic Protip: Avoiding Hydrated Lime If you love your lawn and the people that use it, avoid hydrated lime. It’s used for softening water and in the building industry and is far too caustic for use on lawns. It burns skin, eyes, and grass alike, and is never the right type of lime to use on your turf.
An Applicator or Rotary Spreader
It’s best to avoid handling any lime product with your actual hands. The whole point of using lime is that it is alkaline – that is, caustic.
It’ll cause skin irritation, so your best recourse is some kind of spreader. These will do the hazardous part of the job for you. They’re often called ‘rotary spreaders’ as they use a spinning element to get the pellets.
These small, handheld spreaders can apply lime to small areas or hard-to-reach spots. They are typically inexpensive and easy to use.
These are larger spreaders pushed by hand and typically have a larger capacity than hand-held spreaders. They are best suited for small to medium-sized lawns or gardens.
These spreaders are designed to be attached to a lawn tractor or ATV and can cover large areas quickly and efficiently. They are best suited for large lawns or fields.
These spreaders release the lime from the bottom, allowing precise control of the application rate and distribution pattern.
These spreaders release the lime from the top, allowing the lime to be distributed over a wide area. If you have huge areas of lawn to get done, a broadcast spreader will get the job done in very little time.
You’ll need to break up the soil enough so that the applications of lime get down to the soil rather than settle on the surface of the soil.
An aerator is rolled over the surface of the lawn and pokes holes in the surface of the lawn, allowing air and other substances down to the roots.
Personal Protection Equipment
When handling any sort of strong soil amendment, always wear protective gear. Lime is especially hazardous, so you will need to use:
- Dust Mask
I’m just as guilty as anyone of the occasional bare-handed application of fertilizer, especially organic ones like manure or compost, but for lime, you don’t want to mess about. It’ll cause chemical burns in no time.
Step-by-Step Lime Application
Step 1: Test the soil
How much lime you put on a square foot of lawn can change based on the soil and the kind of lime you use. I can’t stress enough how important it is to run a soil test before you start flinging lime around.
The soil pH level will give you the correct amount of lime to apply. Add too much, and you can push the pH of your soil out of that neutral band. Too little, and frankly, why bother?
Step 2: Determine the amount of lime needed
Once the soil pH has been determined, you can calculate the amount of lime needed to raise the pH to the desired level.
This information should be printed on the lime packaging, but you can consult a local gardening expert, like the University Extension offices mentioned above.
Generally, a good starting point is to apply between 40 and 50 pounds of lime per 1,000 square feet of lawn.
Step 3: Aerate your lawn
Before applying lime to an established lawn, aerate it using a core aerator. The more thoroughly you aerate, the more efficiently the lime will function.
Step 4: Spread the lime
Broadcast the lime evenly over the entire area that requires treatment.
Step 5: Water the lawn
After spreading the lime, it is vital to water the lawn thoroughly to help the lawn lime percolate into the soil.
Step 6: Wait for the results
It may take several weeks for the lime to take effect and for the pH to rise. If you don’t see results, wait at least 6 weeks before retesting the soil pH.
When is the Best Time to Lime a Lawn?
The best time to apply lime to a lawn is in early spring. This allows the lime to be absorbed by the soil before heavy rainfall and the next growing season.
Using lime in early spring ensures that the lawn has the nutrients to promote healthy grass growth during the summer months and to withstand whatever punishment the hot weather brings, up to and including summer sports, barbecues, and the like.
Some folks like to cheat and add grass seed to their lime. I personally don’t think it’s a good idea, as the lime doesn’t have a chance to do its job before the seed sprouts. One thing at a time is often the best way to go about it.
Applying lime in the summer may become necessary, but try to avoid it if you can. Applying lime during this time can stress the lawn and stunt its growth. But if the pH is shot and you absolutely must apply lime in the summer, protect your lawn from stress.
Apply the lime in the early morning or late evening to avoid the day’s heat. Watering the lawn after the lime treatment is also vital to help the lime be absorbed into the soil, in addition to keeping it well hydrated.
I also suggest you use less lime, no more than 5 pounds per square foot, to avoid over-liming and knocking the pH too far up for a healthy lawn.
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