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If you’re wondering how to tell if your lawn needs lime, keep reading for my visual and soil tests. I also cover what causes soil to become acidic in the first place and how to apply lime for the best effect.
What is lawn lime?
Lawn lime is a soil amendment made from ground limestone rocks. These rocks are composed mainly of magnesium carbonate (MgCO3) and calcium carbonate (CaCO3).
Adding these compounds to your lawn raises the pH of the soil, making it less acidic. This increases the availability of essential nutrients and promotes overall lawn health.
Why is lime good for my lawn?
Low soil pH can inhibit microbial activity and cause deficiencies in key nutrients like nitrogen, phosphorus and potassium. This ultimately leads to an unhealthy lawn that’s more susceptible to stresses like heat damage, droughts and weeds. Lime neutralizes acids in your soil and increases the pH. This has several benefits including:
- Increasing microbial activity and nutrient availability
- Accelerating the decomposition of thatch, which if left too long can harbour disease and fungus spores
- Boosts the effectiveness of fertilizers
- Encourages the grass to develop a stronger, more resilient root system
How to tell if your lawn needs lime?
Soil testing is the best and easiest way to understand if your lawn needs a lime application or not. There are also some more visual clues you can look out for, such as particular weeds growing in your grass.
Most of the physicals signs are general indicators of poor lawn health, so spotting one of these on their own doesn’t automatically mean your soil is too acidic. If your lawn displays several of the symptoms, or you live in a region with naturally acidic soil, then you can be more confident it’s suffering from a low pH.
Here are seven ways to tell if your lawn needs lime.
A soil pH test shows a pH level lower than 6.5
This is the most definitive way of understanding if your lawn would benefit from a lime application.
Doing a soil test will tell you the exact pH of your soil and therefore if it needs lime or not.
pH is a measure of how alkaline or acidic the soil is. 7 is neutral, below 7 is acidic and above 7 is alkaline. The ideal pH for your soil will vary depending on what type of grass you have, generally speaking it should be between 5.8-7 (slightly acidic). Cool-season grasses prefer to be at the lower end of the range, while warm-season grasses are happier at the higher end.
The ideal pH for most grasses is 6.5. Therefore, if the results show a pH of less than 6.5 your lawn would benefit from a lime application.
There are multiple different ways of testing your soil. I discuss these in more detail further on in the article.
You have lifeless, yellow grass
One of the most obvious signs that the pH balance of your lawn is off is yellow grass that doesn’t seem to be growing.
Also, grass that’s having trouble bouncing back from drought or a heatwave is a telltale sign that your soil needs a lime treatment.
Because acidic lawns are deficient in nutrients, they struggle to recover from stress and can end up thin, patchy and dead looking.
Your lawn is overrun with weeds
Excessive weed growth is a sign of an unhealthy lawn. When grass is in a weakened state it’s easy for weeds to overtake.
Paying close attention to the type of weeds that are growing can give you an idea of the problem that’s causing them.
Here are some common weeds that may suggest your lawn needs lime:
- Broadleaf plantain
- Common mullein
- Oxy-eye daisies
- Stinging nettles
- Wild strawberries
All of the above weeds thrive in acidic soil. If you notice a few of these in your lawn then you can be pretty sure that your lawn needs lime.
Moss is growing in your lawn
The appearance of moss in your lawn is a visual clue that your grass isn’t getting the nutrients it needs. One thing we know inhibits nutrient uptake is a low pH.
Moss grows very well in acidic soil so is a good indication of high soil acidity.
Fertilizers aren’t working as you’d expect
If you find yourself having to add more and more fertilizer to see any sort of effect, then your lawn could be too acidic.
Acidic lawns can’t absorb nutrients. No matter how much nitrogen you throw at the grass, it’s not going to make a difference – this can sometimes even lead to people over-fertilizing.
You live in an area prone to acidic soil
If you live in the Eastern, Southern or Pacific Northwest region of the U.S then you’re soil will be naturally acidic, and is more likely to need a regular lime treatment.
These areas have higher rainfall and more acidic organic matter decaying. Both of these factors lead to increases in soil acidity.
You have pink hydrangeas
Hydrangeas are excellent flowers to grow if you want a visual indicator of the pH of your soil.
The flowers change colour depending on the pH of the soil they’re grown in. They’ll turn pink in acidic soil and blue in basic soil.
How to do a soil pH test
As I explained earlier, the most reliable way to answer the question ‘how to tell if your lawn needs lime’ is to do a soil test. If the pH level is lower than 6.5 then your lawn could benefit from applying lime.
There are three different ways to conduct a soil test:
- Take a soil sample and send it to be tested at your local county extension
- Use a home testing kit
- Conduct a DIY soil pH test
Sending off a sample of your soil will give you the most accurate results. The results will also inform you exactly how much lime you need to apply, as well as what type of soil you have and any additional amendments you need.
Using a home soil test kit is the simplest option. You can either use strips or a pH meter. Both of these can be purchased online. The results from these tests are instant and will tell you the pH of the soil, but not how much lime you need to add.
A DIY test is cheap and easy to conduct. But the results only give you an indication of the pH level of your soil, not an exact measurement.
- 1/2 a cup of vinegar (any kind you have at home will do)
- 1/2 a cup of baking soda
- two containers
- soil sample
I conducted the test on my soil at home, and have posted the results below each step.
Step 1: Split your soil sample between the two containers
Here’s a picture of the equipment I used. I used red wine vinegar but any vinegar you have at home will work.
Step 2: Add the vinegar to one of the soil samples. If it sizzles your soil has a basic pH level (alkaline).
In my test, there was no reaction between the soil and the vinegar – so I don’t have basic soil.
Step 3: Add the water to the other cup until the soil is mud-like in texture
Step 4: Add the baking soda, if the mixture sizzles your soil has an acidic pH level and it needs a lime treatment
Our solution started fizzing and bubbling when I added the baking soda indicating that I have acidic soil.
Step 5: If neither solution reacts your soil is neutral
What causes an acidic lawn?
An acidic lawn might be the norm where you live, or outside influences could have upset the pH balance in your soil. Understanding what can cause your lawn to become too acidic can also help you with understanding how to tell if your lawn needs lime.
Here are five things that can contribute to creating an acidic soil environment.
Sandy soil is bad at holding nutrients. Basic elements like calcium are easily washed away leaving acidic soil in their wake.
Sandy soils need lime applications little and often. The soil’s porous nature means a small amount of lime can quickly raise the pH level, but the lime is swiftly leached away and needs to be reapplied.
Clay soil is stickier and requires much more lime to balance an acidic pH. But once the pH of clay soil has reached neutral, it’ll stay like that for much longer.
Ammonium based nitrogen fertilizers release acidic hydrogen cations into the soil as they work. Over time this lowers the soil pH until eventually, it’s so low it needs a lime treatment.
If you live somewhere with naturally acidic soil, you can reduce how often you have to lime your lawn by using organic fertilizers. Urea and compost are less acidifying than ammonium-based fertilizers.
Rain and heavy watering
One of the reasons Eastern, Southern and Pacific Northwest regions have naturally acidic soil is because they experience high levels of rainfall.
Both rain and excessive irrigation will increase the rate at which alkaline elements like potassium and calcium leach out of the soil. This, in turn, creates a more acidic environment.
If you live in an area that experiences acid rain then it’s almost a certainty that you need to apply lime to your lawn.
Acidic organic matter
Eastern, Southern and Pacific Northwest regions also tend to have more trees. Leaves and pine needles are acidic in nature. As they decay, they cause the surrounding soil acidity to increase.
Even if you don’t water excessively and use compost as fertilizer, a healthy lawn will still gradually acidify the soil.
Healthy grass will use alkaline nutrients from the soil to grow, eventually depleting them to low enough levels that you need to apply lime. The increased microbial activity associated with good lawn care will also gradually create a more acidic environment.
When to apply lime?
Spring or fall is the best time to apply lime, although you can apply it any time of year as long as the ground isn’t frozen.
Fall is preferred by most gardeners because this coincides with the overseeding season. The increased rainfall over winter and the cycles of freezing and thawing helps the lime to breakdown and penetrate deep into your soil.
Lime shouldn’t be applied to an overly wet or dry lawn. Wait for a period of dry, cool weather and water your lawn to moisten the soil just before applying the lime.
How to apply lime?
To give your lime the best chance of working it’s best to apply it after you’ve aerated the lawn. Aeration enables the lime to reach deeper into your soil, where it’ll be more effective than if you just spread it on the surface.
The quickest way to spread the lime is to use a standard garden spreader. I like Scotts broadcast spreader because it’s easy to use and has multiple use cases.
After you’ve applied the lime, water it down to ensure it’s well incorporated into the soil and not just stuck to the grass.
Lime can take a few months to work, and if your soil had a really low pH then you might need a few applications of lime before the imbalance is corrected.
I recommend testing your lawn every year to check the pH levels. For most lawns, after the initial lime treatment, an application every 3 years will be sufficient.
Types of lime and their benefits
There are broadly two types of lime you can buy for your lawn. These are dolomitic lime and calcitic lime.
Dolomitic lime, also sometimes referred to simply as ‘dolomite lime’ contains both magnesium and calcium. Its use is recommended when your soil is deficient in magnesium as well as suffering from a low pH.
Calcitic lime is derived from deposits that contain mostly calcium carbonate. It lacks the magnesium found in dolomitic lime. If your soil test shows that your soil is not deficient in magnesium then you should use calcitic lime.
You can buy lime in different forms
Lime today is sold in different forms, including:
- Pulverized lime – fast-acting, but the powder tends to clog spreaders and can blow away in the wind
- Granular / pelletized lime – easily spreadable, but takes longer to break down than powders
- Hydrated lime – extremely fast-acting, but not recommended for normal use as it’s very easy to over lime and damage your lawn
What lime do I recommend?
I use Penningtons fast-acting lime for my lawn.
It comes in a pelletized form so is easily applied using a lawn spreader, and you get noticeably faster results.
The pellets combine advanced soil technology with high-quality dolomitic lime to maximize the benefits to your lawn.
Giving your lawn a lime treatment will help keep it looking thick and green all year round.
Make sure to check out the rest of my website for more awesome lawn care tips.