Late summer and fall are good times to apply lime to turf areas. The following are some considerations in liming lawns and turf areas.
Fall is a great time to address soil fertility issues, including liming. Recent soil tests from a reputable lab will give you some guidance on how much (if any) lime would be needed. Two pH figures are reported on a soil test report: pH and buffer pH. The pH figure tells you whether or not you need lime and the buffer pH value tells you how much is needed to reach the target pH for turf (6.0-6.5 for most turf in Delaware).
Raising soil pH is the goal of liming. If magnesium is deficient or low in the soils, those soils may benefit from the application of dolomitic limestone (Hi Mag), though magnesium availability increases with increases in pH; otherwise use calcitic lime (Hi Cal).
A few other things to keep in mind:
1. Tillage is the best way to incorporate lime when doing a new planting or complete renovation. In existing turf, core aeration is a way to move some lime into the root zone of turf and get better response to liming.
2. If surface applying lime, do not apply urea based fertilizers soon after application of the lime. Urea volatilizes much more quickly on an alkaline surface, and nitrogen is lost to the atmosphere.
3. Calcium deficiencies are extremely unlikely in Delaware and most states in the Mid-Atlantic; apply liming materials to adjust pH up, not to supply calcium (which becomes abundant at optimum pH levels). Most of our soils contain abundant amounts of available calcium, and turf uses only a small amount of calcium.
4. Gypsum does not raise soil pH. This includes waste products like ground wallboard.
Adapted from "Liming Considerations for Late Summer and Fall" Keith Diedrick and Robert Mullen in the current edition of the Crop Observation and Recommendation Network Newsletter from the Ohio State University.