Volume 2.1 pH
Soil pH is a measure of the acidity or alkalinity in the soils. Soil pH is important because it influences several soil factors affecting plant growth, such as (1) micro-organisms that are responsible for breaking down organic matter, (2) nutrient leaching, (3) nutrient solubility, (4) toxicity and deficiency of essential nutrients, (5) suppression and enhancement of soil-borne plant diseases, and (6) soil structure.
Soils are referred to as acid, neutral, or alkaline, depending on their pH levels, with 7 being neutral, below 7 acidic and above 7 alkaline. The pH range normally found in soils varies from 3 to 9. The desirable soil pH range for optimal plant growth varies depending on the crop. Generally, a soil pH between 6.0 and 7.5 is acceptable for most plants as most nutrients become available in this pH range. However, some plants have soil pH requirements above or below this range.
Soil pH is normally measured in a soil water suspension. However, the presence of soluble salts in a soil sample can affect pH, and for this reason, some analysts prefer to measure it in a mixture of soil and 1 M KCl or 0.01 M CaCl2.
The methods to assess pH already harmonized by GLOSOLAN are the following: