pH is a number that tells you whether the soil is alkaline or acidic.
Adjusting the pH refers to changing either one of these by adding lime
of 7.0 is a "neutral" pH. This level or close to it is ideal for
nutrients to be used by the grass. When the pH is too high or too low,
many of the nutrients such as phosphorus and iron are bonded to the
soil and unavailable for the root system to use properly. When this
happens the grass does poorly. More often than not, the lawn will show
no outward signs or symptoms, but if you fertilize your lawn every 4-6
weeks it may not respond well. Having a laboratory test the soil is the
only reliable method of determining soil pH.