SOIL AND PLANT ANALYSIS (1+1)

INTRODUCTION

• Soil acidity refers to presence of higher concentration of H+ concentration in soil solution and at exchange sites. Soil acidity is a major problem in relation to plant growth and therefore acid soils are called as a problem soil. Acid soils are characterized by low soil pH, which varies form strongly acidic (4.5-5.5) to extremely acidic (<4.5) and with low base saturation.


• Soil acidity is of three kinds’ viz., active acidity, exchangeable acidity and residual acidity. The hydrogen ions in the soil solution contribute to active acidity. It may be defined as the acidity developed due to concentration of H and Al ions in the soil solution. The concentration of hydrogen ion in soil solution due to active acidity is very small, implying that only a meager amount of lime would be required to neutralize active acidity. In spite of smaller concentration, active acidity is important since the plant root and the microbes around the rhizosphere are influenced by it.


• The concentration of exchangeable Al and H ions contribute to exchangeable acidity. It may be defined as the acidity developed due to adsorbed H+ and Al3+ ions on soil colloids.


• Aluminium hydroxyl ions and H and Al ions present in non – exchangeable form with organic matter and clay account for the residual acidity.


Total acidity = Active acidity + Exchangeable acidity + Residual acidity