Index >> Soil, Nature Medium For Plant Growth >> Soil pH

The pH os soil determines the mineral content as well as microbial composition. High pH release K⁺, Mg²⁺, Ca²⁺, Mn²⁺, Cu²⁺, and Al³⁺ by weathering processes of soil whereas low pH favours solubility of salts including carbonates, phosphates and sulphates. Generally, fungi are predominant in the rhizosphere under low pH conditions (< 5.5) and beneficial nitrogen fixing microorganisms are favoured by neutral pH. Plants adapt to soil pH and this depends upon species. Plants like rye, oats, potatoes and wheat adjust to pH range of 4.1-7.4. On the other hand, lupines have pH requirements in the limited range of 4.1 to 5.5.

The total ion concentration of these soils are not conducive to plant growth. The degree of salinity is usually measured in the water extracts of soils in terms of electrical conductivity. This is expressed as mm hos/cm which is the reciprocal of electrical resistance. As the salt content increases the electrical conductivity also increases. Salt affected soils are common in many countries with conductivity values in the range of 2-20 mm hos/cm in saturated extracts.