Soil & Lawn pH
pH ranges from 1 acidic to 14 alkaline with a neutral pH of 7 which is neither acidic or alkaline.
pH is one of the more important properties of soils when it comes to lawns or any plant for that matter. Different plants thrive in different pH levels; I’m sure you’ve heard of acid loving plants and ericaceous composts in which to grow them.
pH for Grasses
Grasses like a pH between 5.5 and 7. The low end (slightly acidic) is preferred by your fine lawn grasses (bents and fescues) whilst your broader leaved grasses (rye and meadow grasses) like a more neutral pH at 6.5.
Plant and grass nutrients are most readily available around the neutral pH level. In addition, microbes are at their most active helping to control thatch levels and breaking down organic material. On the downside however, lawn weeds also like a more neutral pH. Because pH can be difficult to adjust accurately and maintain it is generally best to leave it alone if it comes in between about 5.5 and 8. Anything below or above this range may need adjustment.
You don’t have to have a soil analysis done to get the pH of your soil. A simple pH tester can give an approximate quick and easy guide to the pH. If you’re on the limit of the desirable range (pH5 or below and pH8 or above) or you are planning to adjust the pH or you’re going to spend a lot of money on your lawn then I suggest getting a full analysis done.
Other indicators of pH will come in the form of grasses and plants. A lawn with woodrush, sheep’s sorrel or moss with finer leaved grasses doing well is a good indication of an acid soil. A lawn with broader leaved grasses and a variety of broad leaved weeds will tend to be neutral or possibly alkaline.
Lime will adjust the pH from acidic to alkaline. Do not use it unless absolutely necessary - once on you can’t take it off! If you need to raise the pH use ground limestone or ground dolomitic limestone. Your supplier should be able to advise on the amount required to raise the pH by the required amount. As a guide only I have used it at 100grams per square metre to raise the pH by 0.5.
Adding lime should only be considered if you lawn has a pH below 5. Creating too much alkalinity will help weeds and weed grasses establish.
Iron or Ferrous Sulphate will bring the pH down making the soil more acidic though this is usually only temporary. If you need to use this read the label and be careful with quantities and application.