When a lawn or garden is doing less well than we are hoping for, in spite of a lot of time and money spent on planting, fertilizing, and watering, an answer to the question of "what's wrong?" can sometimes be found in the results of a soil test.
To encourage healthy plants, getting the soil "right" is incredibly important. A routine soil test can help by identifying the pH and the balance of major nutrients of the soil in question. In general, soils in Cobb County tend to be more acidic than most turfgrass and garden plants will do well in, but it is actually possible to apply so much limestone to the soil that the pH is raised too high.
When the pH is beyond the most optimal range (which varies, depending on the kinds of plants being grown), the plants are less able to use the nutrients that may have been added to the soil, in either fertilizer or composts.
The value of a soil test, such as one done at the soils lab at UGA, is that it will not only identify the soil's pH and nutrient levels, but it also will provide a recommendation for how much limestone (or not) and specific fertilizers should be applied to benefit the desired plants.
Adjusting a soil's pH is a long-term project. Applications of limestone for raising the pH, or sulfur for lowering the pH, won't make a big difference right away; it takes months to work. If a soil test done now finds that the pH is too low for the desired plants (Bermudagrass, for example), then applying limestone now, or very soon, will give it more time to work ahead of the growing season.
The UGA publication Soil Testing for Home Lawns, Gardens, and Wildlife Food Plots provides instructions for taking soil samples, including that about 2 cups of soil should be brought to the local Cooperative Extension office for sending to UGA. Currently in Cobb County, the routine soil test costs $8, as of Jan. 2016, and it can take seven-to-ten days to get the results, which can be returned via either email or U.S. Postal Service.