Understanding Soil pH
Soil pH is a measurement of the ratio of acids and bases in your compost/soil. The measurement scale used for pH ranges from 0-14.
From number 7 and below is considered acidic and from number 7 and above is basic. You may have noticed that number 7 was mentioned two times there. That's because the middle of the scale is balance or neutral.
Knowing the pH levels of your compost is important mainly because of the relationship between pH levels and nutrient absorption through the root system.
A neutral pH allows nutrients to remain soluble long enough to travel through the soil and reach the roots, an off balance pH level will prevent a plants from getting all the nutrients it needs from the surrounding compost.
Most nutrients are completely soluble in the 6 to 7 pH range which is why its the ideal range to keep your plant's soil in.
Many nutrient deficiencies can be corrected by altering the soil pH back to a neutral range. Changes in soil take time to begin to affect the plant so don’t make large changes too quickly or you might find yourself with a more sick plant on your hands.
See below for information on how to measure your pH levels and how to change them.