Soil pH 

What is the pH of the soil? Soil pH is a measure of active acidity based on the concentration of hydrogen ions (H+) in the soil solution. It is an indicator of the current soil condition and is a major factor controlling the presence of nutrients, microbial processes and plant growth. The pH 7.0 is neutral, less than 7.0 is acidic, and over 7.0 is alkaline. It is measured with a pH device. As the acidity increases, the pH of the soil decreases. Maintaining the right pH of the soil is one of the most important aspects of soil fertility management.

When the soil is acidic, there are usually low amounts of calcium and magnesium in the soil and the presence of macronutrients such as nitrogen, phosphorus and potassium is reduced. Most trace elements are more soluble and therefore become more accessible to plants in acidic soil. In very acid conditions, aluminum, iron and manganese can be so soluble as to reach toxic levels.

The acidity of the soil also affects soil germs. For example, when the pH of the soil is low (below 6.0), bacterial activity is significantly reduced. When the pH of the soil is maintained at the appropriate level, the presence of nutrients for the plants is optimized, the solubility of toxic elements is minimized and the beneficial soil organisms are most active.

Although many plants grow best in soil with pH between 6 and 7, there are some remarkable acid exceptions, including blueberries and rhododendron, which are best presented under soil conditions with lower soil pH.