Posted By SarahV on 3/11/2009 12:17
Most lawns prefer a soil pH of 6.2 to 6.8 which is considered to be neutral soil pH. Soil pH is measured in pH units which range from 0 (highly acidic) to 14 (highly basic). Soil pH can be measured by a simple soil test kit that can be purchased at most local lawn and garden centers. If your lawn is not in the preferred range, it will start to show signs of stunting as the soil nutrients become less available to the grass plants. This will also allow the growth of weeds including dandelions which will start to overcome the less healthy grass. Add lime to your soil to raise the pH and add sulphur to lower the pH. Dandelions prefer a soil pH of 7.5, if you have an infestation of dandelions this could indicate that your soil pH needs to be lowered. A balanced soil pH, can provide the perfect soil enviroment for you to have a lush, thick green lawn. A thick lawn, along with mowing freqently enough helps to ensure that weeds are unable to build up energy reserves and become well established.

Paul,  I can't quite remember where I had read the information that I posted.  I also have a few books that I reference as well.  However, I'll bet if you just do an online search for "lawn pH", you'll get some really good data, as a lot of the University sites have great lawn care data.  Good luck on your reading up!  If you find some additional helpful information, please share it with us!