The Aridisols

Aridisols are our desert soils. They are mainly found in the rainshadows of Haleakala and Mauna Kea. Although quite fertile, they are primarily used for grazing owing to aridity and lack of irrigation water.

The Spodosols

If we move from the driest areas to the wettest spot in the State, we find the only Spodosol in Hawaii. In parts of the Alakai Swamp, soil conditions are just right to move organic matter-bound iron and aluminum down into the subsoil. A vertical cross section would reveal a surface organic layer, followed by a bleached horizon showing little trace of discoloring iron oxide so commnon in our soils, and finally an ashy colored horizon of humus accumulation. Spodosol derives its name from spodos which is the Greek word for wood ash. Spodosols are commonly associated with temperate evergreen forest and are not common in the tropics.

The Entisols

If Inceptisols are juvenile soils, the Entisols are infant soils. Their extreme youth is indicated by the prefix Ent- borrowed from the word recent. In Hawaii we have recent soils developing on beach sand. They are called Psamments which is derived from the Greek word Psammos meaning sand. The Jaucas (pronouced hauca) series found along the North Shore of Oahu and the neck of Maui is an example of a psamment. The Spanish name originates from Puerto Rico where the soil was first identfied.

Entisols are also commonly found in river deltas where new land is created by sediment deposition from annual floods. Some of the world's most productive soils are Fluvents which are Entisols formed by fluvial processes. The ancient hydraulic societies that emerged along the Tigres, Euphrates, Nile and Indus rivers were supported by the richness of Fluvents.

The principal criterion for placing a soil into the Entisol order is the absence of organization of soil materials. They show little or no structure or horizon development and resemble material in a pile of freshly screened sand or soil.