Healthy lawns will generally have a pH between six and seven. If your soil’s pH has tested below these numbers it means your soil is acidic. When lawn soil is acidic, the soil does not have enough of the necessary nutrients it needs for proper plant growth. These nutrients can include potassium, phosphorus, nitrogen, sulfur, calcium, molybdenum and magnesium. As these nutrient levels drop off your lawn will start to lose its tolerance to stress and its color. Adding lime to your lawn increases the availability of these nutrients.
Lime is pulverized chalk or limestone. Its active component is calcium carbonate, yet it may also include magnesium carbonate, magnesium oxide and calcium oxide.
Adding lime to your lawn will increase the soil’s pH. This means your grass and plants will get the nutrients it needs to grow better. Adding lime to an acidic lawn will also improve water penetration.
You should not add lime to your lawn unless you have had a soil test done on your lawn and it indicates your lawn soil is acidic. Many people add lime to their lawns annually and this can make lawn soil have a very high pH, or make soil alkaline. This is just as bad as having acidic soil and should be avoided.