Ammonia Volatilization From Soils: Equilibrium Considerations

Abstract

The volatilization of ammonia from soils as a function of the system's properties is analyzed theoretically and experimentally. The final concentration of ammonium held by the soil increases with an increase in hydrogen ion activity, with the initial ammonium concentration, and with partial pressure of ammonia in the air. An increase in the buffer capacity of the soil leads to a decrease in the final ammonium concentration.A good agreement has been found between measured and computed values for NH₃ and NH₄ concentrations during the process.The pH of the soil is the dominant factor controlling the extent of ammonia volatilization only when the soil's buffer capacity is high, or, when the concentration of ammonium in the soil is low. At high pH and high initial ammonium concentrations, the dominant factor controlling the reaction is the buffer capacity of the soil.