pH
pH is a way of measuring how much acid and alkaline is in the soil. The pH scale runs from 1 - 14. 7 is neutral, 0 is very acidic and 14 is very alkaline. Cannabis plants in soil like a pH of 7. When choosing your soil you should be looking for a pH of 7. It should tell you this on the bag. Going above or below this mark can cause your plant problems during growth. Small pH meters can be bought in most gardening shops and can be used to measure the overall pH of your soil.
It is always good to check the pH at least once every week for plants that grow in soil. It is also good to check the soil’s pH a day or two after you feed your plant.
If you find that your soil’s pH has shifted out of the 6 - 8 range you may want to try and bring the pH back to 7. Again, below 7 is acidic and above 7 is alkaline. There are two ways to do adjust the ph of the soil. The first is called a soil flush and is not recommended but may be needed under certain circumstances such as serious pH fluctuations and chemical burns.