Soil and Plant Analysis

Sodic soils

Sodic soils are having high proportion of sodium at exchange complex. The sodium ion at exchange complex usually exceeds 15 percentage in these soils. These soils also have high proportion of precipitated insoluble carbonates and bicarbonates and hence the pH always more than 8.5. On contrary degraded sodic soils have low pH at surface but exchangeable sodium percentage is more than 15 and they do not have precipitated CaCO3. Sodic soils are formed due to the soil forming process of alkalization (accumulation sodium in soils) while solodi solids / degraded alkali (sodic) formed by the process called solidization.
Effect of soil sodicity

Since these soils have high amount of CO3 and HCO3 and high pH, Carbonate, bicarbonate and OH (hydroxyl) ions injuries on plants are observed. High sodium in clay becomes reason for dispersed nature of clay under wet moisture regions.
Dispersed nature of the clay leads to soapy feeling of soils, stagnation of water, poor infiltration/ percolation and poor aeration. Sodic soils become hard mass during dry periods.
These soils have poor workability both under wet and dry seasons.
Further hazardous effects of Na on plants are also seen. Sodium carbonate with water releases Na+, HCO-3 and OH- ions, which are harmful to growing plants.


2 Na+ + CO32+ + H2O → 2 Na+ + HCO3- + OH-


High pH is also unfavorable for the growth of microorganisms.
Low microbial activity causes slow decomposition of organic matter and hence nutrient availability is also affected specifically nitrogen, sulphur etc.
Since these soils enriched with high Na at exchange complex, Ca and Mg availability are also less.
High pH becomes the reason for non-availability or less availability of Fe and Zn.
Deficiency of Zn is common in this soils.
Phosphorus availability is also less due to conversion of phosphors into insoluble calcium and magnesium phosphates.
All the above effects on plants result in drying of plants in patches in a field. Under extreme conditions no plants are seen in these soils.