Question: My dad always put lime on our lawn every year when I was growing up. My wife and I just moved into our first house, and I’d like to know if I should be following in my dad’s footsteps and putting lime down on the lawn every year, too. What’s the benefit of adding lime and what happens if I don’t add it?

Answer: Here in Western Pennsylvania our soils are clay-based and they’re often fairly acidic. Your dad added crushed limestone (lime) to the lawn to help neutralize the acidity of the soil there and make it more hospitable for lawn growth. Before you decide whether or not you want to follow in your dad’s footsteps, here’s why soil pH is so important and some tips for adding lime correctly, should you decide to do it.

The pH scale runs from 0 to 14, with measurements in the 0 to 7.0 range being acidic, and those above 7.0 being alkaline. A pH of 7.0 is neutral. The pH of your soil is so important to plant growth because it determines the availability of almost all essential plant nutrients.

When soils are too acidic, certain nutrients become less available (phosphorus in particular), beneficial soil bacteria are less active and certain elements — like aluminum and manganese — can become toxic. This is true regardless of whether you’re growing veggies, lawns or flowers.

Since our soils here in Western Pennsylvania tend to lean toward the acidic side, lime is used to raise the pH and make it less acidic. Our goal is to add just enough lime to adjust the pH to 6.5, but not too much or we’ll tip the pH scale too far. 6.5 is the pH at which the highest number of nutrients are available in optimum amounts. If you’re growing evergreens, an acidic pH is ideal, but for lawns, flowers and vegetables, the target is 6.5.

Get it tested

The only way to tell if your soil’s pH needs to be adjusted, and the proper amount of lime to add to do it, is to get a soil test. They can be purchased through your county’s office of the Penn State Extension Service.

While for many years homeowners regularly doused their lawns and gardens with a random amount of lime, we now know how important it is to know your starting pH before adding any lime. Otherwise you could be wasting money and over-shooting your ideal pH target by adding too much, or your liming could be a waste of time because you didn’t add enough to effectively change the pH.

The soil test will not only tell you the current pH of your lawn’s soil, it will also tell you how much lime to add to “fix” the pH. You should test and adjust your soil’s pH every four or five years because eventually it will revert back to its natural number.

Which kind?

Next, if you decide to lime your lawn, it’s important to understand that not all liming materials are created equal. First, look to your soil test results to determine if you need calcitic lime or dolomitic lime.

• Calcitic lime is mined from natural limestone deposits and crushed to a fine powder. It is also called aglime or agricultural lime and supplies calcium to your soil as it adjusts the pH.

• Dolomitic lime is derived in a similar manner but from limestone sources that contain both calcium and magnesium.

If your soil test came back showing high levels of magnesium, use calcitic lime. If the test shows a magnesium deficiency, then use dolomitic limestone. Clay soils tend to hold onto magnesium, so more often than not, calcitic lime is the more appropriate choice for gardeners in Western Pennsylvania.

Next, look for pelletized calcitic lime. This product is created by taking the finely pulverized particles of lime and binding them together with a binder compound to form small pellets. Pelletized lime is much easier to spread than powdered lime products and will keep you from getting covered with dust. Uniform coverage is very important as lime is insoluble and can’t move around within the soil. Skipped areas won’t have an effective pH change, and overlapped areas will undergo a more drastic pH change. To cover the area evenly, spread half the pelletized lime in one direction over the entire area, then apply the rest in a perpendicular fashion, creating a crisscross pattern.

Pelletized lime is only slightly more expensive and is well worth it for its ease of application and convenience. If your soil test recommendations came back with application rates for crushed agricultural lime, the application rate for pelletized lime is lower. Apply at a 1:10 ratio. Meaning you need 10 times less pelletized lime than agricultural lime to garner the same pH change. For example, if your soil test recommends adding 100 pounds of agricultural lime, add 10 pounds of pelletized.

All that being said, there’s no rule that says you ever have to lime your lawn. Many lawns perform just fine even with a less-than-ideal soil pH. For me, the proper soil pH is much more important in my vegetable garden, where a pH too far away from the ideal can affect yields and veggie size. I do test my vegetable garden’s soil every four years and lime there as necessary. As for the lawn, the decision is yours.

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