A soil classification system is proposed, based on the aeration and hydration capacities of profiles. Hydration is measured by the available water (field capacity minus wilting point), and aeration evaluated by the connection of available air (total porosity minus field capacity) values and steady state infiltration rate. On this basis, 10 soil orders and 28 soil classes are defined. Input variables are: density of solids, bulk density, porosity, field capacity, wilting point, and steady state infiltration rate. The classification is based on strictly numerical criteria, and there are no components of subjective evaluation. The nine principal orders, containing three classes each, are: aerated-aquiferous soils (I); aerated-mesaquiferous soils (II); mesaerated-aquiferous soils (III); mesaerated-mesaquiferous soils (IV); aerated-aquicludeous soils (V); mesaerated-aquicludeous soils (VI); unaerated-aquiferous soils (VII); unaerated-mesaquiferous soils (VIII); unaerated-aquicludeous soils (IX). One last order is possible (order X): the flooded soil order, with only one class. The methodology is applied by selecting soils from literature with varying textural classes, from sands to very fine clayey soils. It is demonstrated that there is no direct relation between the textural class and the soil system class or order. It is suggested that the methodology could also be utilized as a tool for soil management or for the evaluation of agricultural capability of lands where other information (meteorological, phythological, topographic, and management level) is included. Furthermore, the methodology contains useful information for irrigation system projects.
soil classification; available water; soil aeration; steady state infiltration rate
