Why, When, and How to Apply Lime to your Lawn

In many parts of the country, adding lime to your lawn is as essential as mowing it. Without lime, lawn grasses may be unable to benefit from the nutrients in your soil, including those you add through fertilizers. By understanding how lime helps lawns and why you may need lime, you can help your lawn reach its full potential. The following questions and answers can help guide you through that process, so you can lime your lawn confidently:

1. What is Lime?

Lime is a soil amendment made from ground limestone rock, which naturally contains calcium carbonate and magnesium carbonate. When lime is added to soil, these compounds work to increase the soil's pH, making soil less acidic and more alkaline. Even though lime includes calcium and magnesium, which are essential nutrients for healthy plant growth, it's not a substitute for fertilizer. Lime's primary role is to alter soil pH and offset soil acidity, which can improve the availability of plant nutrients.

2. Why apply Lime?

Lawns need lime when low soil pH starts inhibiting the availability of nutrients. Soil pH preferences vary between regional lawn grasses, but most grasses prefer soil pH between 5.8 and 7.2. Warm-season grasses tolerate slightly lower pH, while cool-season grasses prefer pH slightly higher. When within preferred pH ranges, the nutrients lawn grasses need most — including added nitrogen from lawn fertilizers — stay available for grass to use. When pH strays too far in either direction, even plentiful nutrients are restricted. Lime restores balance in overly acidic soil to bring pH back to optimal growing levels.

3. How do I know when my lawn needs Lime?

When soil becomes too acidic, lawn grasses struggle and plants that flourish in acidic soil take their place. For example, the presence of lawn moss signals your soil pH has become too low for strong, healthy grass growth. Other warning signs include increases in common lawn weeds, diseases and insect pests. Many weeds prefer acidic soil, and low soil pH can inhibit the effectiveness of some herbicides and insecticides. When soil is overly acidic, you'll also notice that grasses don't respond to quality lawn fertilizers with the healthy, lush growth you normally expect.

4. Why soil testing is important.

Soil testing provides an accurate measure of your soil's current pH level and other factors, such as soil type, that affect the amount of lime or other soil amendments it may need. Without soil samples, you can't accurately judge your lawn's needs. Applying lime when it's not needed or applying too much can harm lawn grasses instead of help them. If your soil is overly acidic, you should retest every year until proper balance is restored. Established lawns should be tested every three to four years.

5. Why does soil pH continuously change?

Soil pH changes for many reasons, including the lime or other products you add. In areas with heavy rainfall, calcium naturally leaches away as rainwater passes through soil. The loss of calcium means soil pH drops and soils become acidic over time. In these regions, lime is usually a necessity for healthy lawns. In areas with very little rainfall, calcium doesn't leach away, and lawns can become too alkaline. Proper lawn maintenance also naturally lowers soil pH over time. Regular fertilization, proper irrigation and increased activity of beneficial soil microorganisms all contribute to gradual, normal drops in soil pH.

6. When is the best time to apply lime?

Fall and spring are generally the best times to lime lawns. Fall has an added advantage, as rain, snow and cycles of freezing and thawing help lime break down and begin to work.

7. How much lime should I apply, and what's the most effective method?

Soil test results will include the amount of lime your lawn needs, based on its soil type and current pH. Follow those recommendations closely, as acceptable amounts can vary significantly for soil types. For example, clay soil takes much more lime than sandy soil to achieve the same results

8. Calcitic vs Dolomite Lime

On the surface, Calcitic lime and dolomite lime seem like very similar products. They are both made from pulverized limestone and both are effective at raising the pH in acidic soils. So what exactly is the difference between dolomitic and calcitic limestone?

Dolomite lime contains large amounts of magnesium along with calcium carbonate while calcitic lime only contains calcium carbonate. Magnesium is an important mineral for plant health. And if soil needs magnesium, wouldn’t it be best to just use dolomite lime all the time, just in case? Not if too much magnesium can also be a problem. To keep a proper balance of magnesium in your soil, you need to be careful when selecting the proper lime for your lawn.

Magnesium deficient plants are often yellower, have shorter root systems, and produce noticeably lower yields than plants grown in healthy soil.

Too much magnesium can cause your soil to become overly compact, deterring crop growth while also making the soil more difficult to water efficiently. It can also fuel rampant weed growth, further impeding the growth of your crops.

Magnesium needs in your soil often correspond with your soil consistency. Magnesium deficiency is much more common in quick draining soils, especially those that are sandy, while clay and clay loam soils rarely suffer from magnesium issues.

If your fields contain a large amount of clay soil, it is unlikely that you will want to use dolomite lime. In fact, because dolomite can make soil compaction worse, an ill-advised dolomite application can seriously harm denser clay soils.

Calcitic lime has long been the preferred treatment for acidic soil. The main “ingredient” in calcitic lime is calcium carbonate, which is why many people ask if calcium carbonate is the same as limestone. It counteracts the acidification of field soil. Acidification is the natural result of nitrogen heavy fertilizing practices. By adding a lime treatment, you can undo the damage caused by nitrogen treatments without counteracting the benefits. Calcitic lime also works more quickly than dolomite lime: Calcium carbonate is better at balancing pHs than magnesium carbonate, and calcitic lime contains much higher levels of calcium carbonate than dolomite lime.

When applying a calcitic lime, you must till the soil immediately after the lime application. Lime sitting on the surface of your soil will not be nearly as effective as lime that is well mixed into the soil.

But the main drawback to calcitic lime is its simplicity. It is designed to neutralize pH and replace depleted calcium in the soil, and it won’t replace depleted magnesium.

By liming your lawn when it's needed, you help ensure your grass gets the nutrients and advantages it needs for lush, healthy, beautiful growth. Pennington and the line of lawn and garden productsPennington are dedicated to helping you give your lawn the best care possible, so you can grow and enjoy it to the fullest.

Have more questions? Give us a call @ (780) 459-6699