Homeowners apply lime to lawns to correct excess soil acidity. Most turf grasses do best when soil pH is slightly acidic, between 6.0 and 7.0. When soil pH falls into the strongly acidic range below 6.0, rainfall leaches out vital nutrients such as potassium, magnesium and calcium, causing lawns to lose color, vigor and ability to recover from stress. Lime, or calcium carbonate, not only corrects soil acidity but also increases beneficial bacterial activity and nutrient availability.
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Rely on Testing
Lime application should be made only if soil testing indicates a need for lime. The simple soil pH test kits sold through home and garden centers can indicate a need for lime but may not show how much to apply. For that, submit a soil sample to a commercial or state soil testing lab and request the lime quantity your lawn needs per 1,000 square feet, which is the area of a square 31.5 feet on a side. The lab report will tell you how many pounds of pure calcium carbonate to apply per 1,000 square feet to neutralize your lawn’s excess acidity. If the recommendation calls for more than 100 pounds of pure lime per 1,000 square feet, apply half the recommended amount in the fall and the other half six months later.
Because most liming materials are not pure calcium carbonate, you must calculate the actual amount of liming product you'll need. For instance, if the soil test recommends 75 pounds of pure calcium carbonate per 1,000 square feet, and your liming product's calcium carbonate equivalent is 80 percent lime, divide the recommended pounds by the percentage of lime in your liming product. In this example, dividing 75 by 80 will give you 0.9375. Multiply the result by 100 to get the pounds of liming product you need to apply. In this example, you'll need 94 pounds of your product per 1,000 square feet. Don't overapply. Too much lime can drive soil pH above 8.0, or strongly alkaline, which also interferes with grass plants’ nutrient uptake.
Lime for lawns comes in several different forms. The safest common forms are ground limestone, pelletized limestone and dolomitic limestone. Besides neutralizing excess acidity, limestone also supplies plants with calcium, while dolomitic limestone provides magnesium as well. Other forms include burned lime, also known as quicklime, and hydrated lime, also known as slaked lime. These concentrated forms of lime can provide fast correction of soil acidity but are not recommended for homeowners' use because they are hazardous to handle and can burn the grass.
Spread in Fall
The fall is the best time to spread lime. This allows the weather to work the lime down into the soil before spring grass growth starts. A push-type lawn spreader makes liming your lawn easier. There are two types. The drop spreader meters out the product from a hopper and drops it between the wheels, directly on the ground. The rotary spreader’s hopper drops the product onto a spinning disc that throws it out to both sides. Before filling, be sure the spreader is turned off. Set the spreading rate according to directions on the lime product you are using. The spreading rate will vary according to the purity of the product. If you have no directions, set the spreading rate midway between the minimum and maximum rate.
Apply Header Strip
Fill the hopper of your spreader on a driveway or other hard surface so you can easily sweep up any spilled lime. Wear gloves, eye protection and a breathing mask when handling and spreading lime so you don't get it on your skin, into your eyes or in your lungs. Start liming by applying a header strip around the edge of your lawn. Then go back and forth across your lawn in the longest direction. Turn your spreader around in the header strip, shutting off the flow of lime as you enter the header strip and turning it on again as you leave the header strip. Be sure to slightly overlap the edges of each strip as you move across the lawn.