Buffering of Soils

After reading this article you will learn about the buffering of soils.

Buffering of soils is their resistance against any change in the concentration of hydrogen or other cation in the soil solution. For example, the clay micelle is almost completely saturated with hydrogen ions in strongly acid soils which also contain some in the soil solution.

The hydrogen ions absorbed by the micelle (Reserve of Exchange acidity) are in equilibrium with the hydrogen ions present in the soil solution as shown below:

When limestone is added to the soil it first neutralizes the active acidity as shown below:

The buffering capacity or inorganic or mineral soils depends mainly on their texture. Since clay can adsorb ions and not sands. The buffering capacity of soils increases when their percentage of clay increases i. e. their texture becomes finer.

The buffering capacity of soils also depends upon the nature of clay and humus of soils. The buffering capacity of black cotton soils, dominated by smectite group of clay minerals, is much higher than those of red soils which are dominated by the kaolinitic group of clay minerals and hydrous oxides of iron and aluminum.

When the buffering capacity of the soil is very high, larger quantities of nutrients in the form of fertilizers can be added to soil at longer intervals because they will be retained by the clay micelle and not washed down. Similarly more lime is to be added to clayey soils of a high buffering capacity, in order to control the reserve of exchange acidity of soils. Soil pH is very stable in the soils of high buffering capacity.