Soil pH is a measure of the acidity or basicity of a soil. Soil pH is a key characteristic that can be used to make informative analysis both qualitative and quantitatively regarding soil characteristics. pH is defined as the negative logarithm of the activity of hydronium ions in a solution

Soil pH or soil reaction is an indication of the acidity or alkalinity of soil and is measured in pH units. Soil pH is defined as the negative logarithm of the hydrogen ion concentration. The pH scale goes from 0 to 14 with pH 7 as the neutral point.

Acid soils have a pH below 7 and alkaline soils have a pH above 7. Ultra-acidic soils (pH < 3.5) and very strongly alkaline soils (pH > 9) are rare

Effects of soil pH on plant growth? 

In soils that are highly acidic or highly alkaline, key minerals and trace elements may not be available in sufficient quantities for plants to grow properly. Extremes in pH levels can also mean high concentrations or more accessible forms of minerals such as aluminium, which can be toxic to plants.

Effects of Soil pH on microbial process

In addition, pH levels affect the microbial processes that allow organic matter to decompose and deliver nutrients to the soil. In general, a neutral pH provides the best conditions for microbial action that makes nitrogen, sulfur and phosphorus available in the soil.

While most plants thrive best in neutral soils, certain species have a preference for more acidic or more alkaline conditions, depending on their nutritional needs.

Soil pH controls the solubility, mobility, and bioavailability of trace elements in plants.

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Soil pH controls the solubility, mobility, and bioavailability of trace elements in plants which determine their translocation in plants. This is largely dependent on the partition of the elements between solid and liquid soil phases through precipitation-dissolution reactions as a result of pH-dependent charges in mineral and organic soil fractions. For instance, negative charges dominate in high pH whereas positive charges prevail in low pH values. Additionally, the quantity of dissolved organic carbon, which also influences the availability of trace elements, is controlled by soil pH. At low pH, trace elements are usually soluble due to high desorption and low adsorption. At intermediate pH, the trend of trace element adsorption increases.