What is soil Ph
Soil pH is the degree of acidity or alkalinity of the soil.
PH stands for potential of Hydrogen i.e. the concentration of hydrogen ions in the soil. It is calculated using the formula,
pH = – log H+ OR pH = log [1/H+}
The degree of acidity depends on the concentration of hydrogen ions,
When the soil is acidic; hydrogen ion concentration exceeds hydroxyl ion concentration.
When the soil is neutral, hydrogen ion concentration equals hydroxyl ion concentration.
When the soil is alkaline or basic, hydroxyl ion concentration is greater than hydrogen ion concentration.
The pH scale
pH ranges from 1 to 14
pH 7 is neutral
Above pH 7, the soil is alkaline or basic.
Below 7, the soil is acidic.
Causes of soil acidity
Presence of acidic soluble salts which may arise from fertilizers, weathering of minerals etc.
Leaching of bases which are later replaced by hydrogen ions.
Presence of acidic organic matter.
Acidification due to rain water
Biological activities in the soil
Artificial fertilizers e.g sulphate of ammonia
Uptake of bases by plants
The soil may have been formed from acidic parent material e.g granite
Causes of soil alkalinity
Weathering of limestone.
Addition of bases e.g lime.