Before applying anything to your lawn, have the soil tested by a professional testing service. If your soil test shows that the soil pH is low, add lime according to the test recommendations to the letter. Too much of an amendment can be as detrimental to your lawn as none at all.
Lime amendments come in various forms, from ground oyster shells to liquids. Agricultural ground limestone is the preferred type because it is readily available and can be safely, easily, and accurately applied with a drop or rotary spreader.
There are two types of agricultural ground limestone: dolomitic and calcitic. Both contain calcium carbonate, a grass nutrient, and a neutralizer for acidic soil. Dolomitic limestone also contains magnesium for soil that is deficient in the nutrient. Calcitic limestone does not contain magnesium and should be used if your soil is already high in magnesium. However, adding dolomitic limestone to soil already high in magnesium has not been shown to cause any lawn problems.
For faster results, choose a finely ground limestone. Fine grinds begin to correct the soil pH faster than coarse grinds. Coarsely ground limestone is better suited for use once you have raised your pH to within a desirable range. You can tell fine lime from coarse if you understand the information on the package. The higher the percentage of ground lime that passes through the finer sieves, the finer the grind. Sieves are graded by number; the higher the number the smaller the sieve holes. Look for a product stating that 50 percent or more of the ground limestone will pass through a number 100 sieve. But be forewarned: Fine grinds can burn grass. Follow the instructions on the package carefully.
One more thing to keep in mind when buying lime is its relative purity. Liming materials are rated according to their Calcium Carbonate Equivalent (CCE). A CCE rating of 100 is equal to pure calcium carbonate; less than 100 indicates less neutralizing ability than calcium carbonate. Account for the CCE when figuring how much lime to apply to your lawn. If the CCE of the product you purchase is 80 and your soil test recommendations assume a CCE of 100, you will need to increase the recommended application rate by 20 percent.
The more clay and organic content in your soil, the more lime you will need to correct the pH. Sandy soils require less lime to raise pH. If you need to add more that 40 pounds of lime per thousand square feet to correct your pH, do it in two or more applications. And don’t apply lime with fertilizer mixed in the same spreader. The resulting chemical reaction will release the nitrogen you want for your grass into the air. After spreading lime, water the lawn to wash the particles off the grass and into the soil.
To lower the pH, add sulfur according to your soil test recommendations. Sulfur amendments are also available in the form of compounds, such as ammonium sulfate. These compounds can be used in place of elemental sulfur, but they can burn turf if used in excess. See the amendment packaging for the amounts that can be safely applied.
Sulfur acts within one month to lower soil pH. To avoid applying too much, don’t try to make your correction in one application. To meet recommended amounts, make several surface applications a few weeks apart and water the grass after each application.