Lime – When do I use it? How much should I use? How often should I apply it?
Let’s start by explaining why lime is used in lawns and gardens…
You may have heard, “Apply lime to sweeten the soil.” Acids have a sour taste and alkalines are sweet. The pH scale runs from 0 to 14, 7 is called neutral. Less than 7.0 is acidic (sour) and greater than 7.0 is alkaline (sweet).
Therefore, the reason to apply lime is to raise the pH, i.e. to make it less acidic. In contrast, sulfur or gypsum is used to lower soil pH.
The soil reaction (or pH) is important because it controls how available nutrients are to your lawn. Most nutrients that plants need are readily available when the pH of the soil solution ranges from 6.0 to 7.5.
Grass species are adapted to a wide range of soil pH. However, optimum growing conditions for common turfgrass species are where the pH is neutral to slightly acidic (7.0 – 6.0).
The only way to know if you should apply lime and how much is by having your soil tested. You can test it at home using a do-it-yourself kit. You will get better results by sending a sample to a private lab or local extension service. The results from a soil test will tell you how much lime to apply.
When to Lime?
Lime can be applied at any time however, for the best results:
Take a soil test before planting a new lawn. Then apply lime when preparing the soil so that it can be tilled in.
If you need to lime an established lawn, apply it in conjunction with core aeration in the fall. Doing this will
help incorporate it into the soil.
How Often to Apply Lime?
Is your lawn sick? thin? Off color? Not responding to fertilizer applications? Take a soil test to determine if the pH needs to be adjusted.
If your lawn is healthy, and vigorous and has been established for several years, there is no reason to apply lime.
Taking a Soil Test
If you intend to send your sample to the land grant university in your state, contact the local Cooperative Extension Service for information and sample bags. If you intend to send your sample to a private testing lab, contact them for specific details about submitting a sample.
- Follow the directions carefully for submitting the sample. The following are general guidelines for taking a soil sample.
- Sample when the soil is moist but not wet.
- For each acre of land to be tested, 10 to 15 sub-samples are recommended. Areas that appear different or that have been used differently should be sampled separately. For example, a separate sample should be submitted for an area that has been in a garden and one that has been in a lawn.
- Obtain a clean pail or similar container.
- Clear away the surface litter or grass.
- With a spade or soil auger, dig a small amount of soil to a depth of 6 inches.
- Place the soil in the clean pail.
- Repeat steps d through f until the required number of samples has been collected.
- Mix the samples together thoroughly.
- From the mixture, take the sample that will be sent for analysis.
- Send immediately. Do not dry before sending.
If you are using a home soil testing kit, follow the above steps for taking your sample. Follow the directions in the test kit carefully.