The Relationship between pH and Ammonia Equilibria in Soil

Abstract

Abstract Investigation of the relationship between pH and NH 3 equilibria in soils revealed that an increase in the concentration of NH 4 + , applied as (NH 4 ) 2 SO 4 , stimulated NH 3 losses from fine‐textured soils at pH's ranging from 4.5 to 7.1. Ammonia volatilization was directly related to the initial pH of the soil and increased with an increase in pH. It was postulated that NH 3 may be volatilized, even from acid soils, due to the equilibrium NH 4 + + OH ‐ ⇄ NH 3 + H 2 O. By using initial concentrations of NH 4 + from (NH 4 ) 2 SO 4 applied, initial pH of an aqueous suspension of the soil and a value K b = 1.80 × 10 ‐5 , values of NH 3 losses were predicted. The linear relationship found between predicted and measured amounts of NH 3 losses from acid as well as neutral soils, was interpreted as evidence of the existence of the proposed volatilization mechanism in soils.