Calcareous Soils *

A soil is considered “calcareous” from the chemical point of view when it is in equilibrium with excess of CaCO₃ at the partial pressure of the atmospheric CO₂. However, still lacking is the definition of this “excess” of soil CaCO₃ content at which the properties of the soils as a medium for plant growth and the culture practices for their utilization for agricultural purposes are affected. In this regard the FAO symposium on Calcareous Soils ¹ recommended that “the concept of calcareous soils be more precisely defined and the description of these soils be expressed in standardized terminology.”