Lime or Not to Lime
How Much Lime Should I Apply Per Acre of Land?
by Herb Kirchhoff, Demand Media
Too much lime can be as bad as too little
Many household lawns can benefit from application of lime, also known as calcium carbonate or limestone. By neutralizing soil acidity, it raises pH to the slightly acidic level between 6 and 7 where most turfgrass species grow best. It takes about 1.2 tons of ground agricultural limestone per acre to raise soil pH by one point in loam soil. Halve that amount for sandy soil and double it for clay soils.
Soil testing is an essential part of pH management. You shouldn’t apply lime without knowing whether the soil needs pH correction and how much it requires. Do-it-yourself soil pH test kits or soil pH meters from a hardware or home center can indicate if lime is needed but not how much to apply to your particular lawn. It’s better to have your soil tested by your state or county cooperative extension service. These agencies not only test pH but also analyze your soil type to make a recommendation on how much lime to apply to raise your lawn’s pH to a desired level.
Bagged or Bulk
If your acre of lawn tests out at a pH of 5, for example, it needs a one-point increase in pH to bring it up to a pH of 6 for turfgrass health. The 1.2 tons of limestone needed to accomplish this change is equal to 48 standard 50-pound bags of ground agricultural limestone. Alternatively, you can buy your ground limestone in bulk at a lower cost per ton if you have a dry, weatherproof location to store it and will be able to spread it soon after delivery.
Types of Lime
There are five different liming materials that vary in potency and safety. Besides ground agricultural limestone, there’s ground dolomitic limestone that supplies magnesium as well as calcium. Both act slowly. Pelletized limestone has been treated to form tiny pellets that are easier to spread and act faster than the preceding two types, but it’s more expensive. These three types are safe to handle and are spread at the same rate. The other liming materials are burned lime and hydrated lime. These act fast and are much more potent than other lime types. You’d need 80 percent less burned lime and 60 percent less hydrated lime to achieve a given pH increase. However, they can cause alkali burns on skin and plant tissue and tend to cake up inside spreaders.
Apply ground limestone any time during the year, except when grass is brown or ground is frozen. Apply with a push-type or tow-behind drop spreader. Water the lawn thoroughly after application. If you need more than a one-point pH correction, split the required amount of ground limestone in half, applying one half now and the remainder in six months. Don’t lime again for at least three years. If applying lime to lawn space being renovated, till the lime into the top 7 inches of soil before seeding.
Acidic Soil Causes
Soil becomes acidic as the result of heavy rains, decomposing organic matter, excess irrigation, use of acidifying nitrogen fertilizers and acidic groundwater. Soil pH below 6 interferes with turfgrass uptake of nutrients such as potassium, nitrogen, phosphorus, molybdenum, magnesium, calcium and sulfur. Turfgrass that is starving for nutrients won’t look its best and will be less able to withstand or recover from drought, heat or heavy traffic.