So, you fertilized, watered, de-weeded ... and the lawn still doesn't look that great. It's probably time to check the soil pH and apply treatments to correct it. Soil pH indicates the level of acidity or alkalinity, which can prevent turf from absorbing nutrients, and also keep good microorganisms from doing their jobs to break down organic matter. Applying treatments for lawn pH is easy, inexpensive and well worth the results.
Test Your Soil pH
Gather a soil sample and have it tested for the pH level. Not much soil is needed - a handful or less - and can be tested in several different ways. Each state has a Cooperative Extension Service Office, and some will do soil testing. The Cooperative Extension Service is part of the U.S. Department of Agriculture, and the state offices usually work in tandem with the state agriculture department or the state university system. If the Cooperative Extension does not do soil testing in your area, they can likely direct you to a commercial soil lab that does. Also, many garden centers and nurseries now sell do-it-yourself soil test kits that are reliable. In addition, a commercial lawn service may also be able to perform a soil test for you. In general, a neutral soil pH is 6.6 to 7.3, and that's what most plants like. Acid soil is usually found where there's heavy rainfall, sandy soil and lots of organic matter. Those places are usually east of the Mississippi River, especially in the West. Highly acidic soils are common in the western coastal states. Alkaline soils occur most frequently where there's light rainfall, and where minerals such as lime and sodium are high.
Treatments for Acidic Soil
Raise the soil pH if tests indicate high acidity (pH below 6.6). The most common treatment for acidic soil is lime. It's usually made from limestone and is sold as gypsum (dolomitic limestone) or ag lime (calcitic limestone). Gypsum, probably the most commonly used treatment, contains about 10 percent magnesium as magnesium carbonate. Ag lime has some magnesium and up to 40 percent calcium as calcium carbonate. The amount of either that you put on your lawn will depend on the pH soil test, and the type of soil you have: sandy, loamy or clay-type. However, don't apply more than 50 lbs. per 1,000 square feet at one time. If your soil needs more liming, do it in separate applications, at least a week apart.
Treatments for Alkaline Soil
Lower the soil pH if tests show the soil is too alkaline (pH above 7.4). Do this by adding an acidic material, such as iron sulfate or elemental sulfur. The amount of acidic material you need will depend on the soil pH and the type of soil, again. Sandy soil takes the least amount, while loamy soil takes more, and clay-type soils require the most. But, never apply more than 5 lbs. per 1,000 square feet of soil at one time. If more than that is needed to correct the soil pH, you must wait four or more weeks before another application.