Soils of Argentina

Every name that appears on a soil survey map —Argiudol vértico, Hapludol éntico, Natracualf típico— explained: what it means, where it is found and how productive it is.

The names follow Soil Taxonomy, the USDA classification used by INTA. They are built from parts: the order gives the kind of soil, the suborder the climate or water regime, the great group the horizon that sets it apart, and the subgroup what makes it differ from the typical one.

The most widespread

Area according to the 1:500.000 national map.

Molisoles

Soil with a thick, dark surface horizon rich in organic matter (the mollic epipedon), with more than half of its exchange capacity occupied by calcium, magnesium, potassium and sodium. It forms under grassland.

Alfisoles

Soil with a clay accumulation horizon (argillic or natric) and good base saturation, but without the thick, dark surface of a Molisol.

Vertisoles

Soil very clayey, with clays that swell when wet and contract when dry: when dry it opens wide and deep cracks, and when wet the layers slide against each other leaving slickensides.

Entisoles

Soil without diagnostic horizons, or almost: recently deposited material (sand, alluvium) or on which the climate did not have time to act.

Inceptisoles

Soil young, with some development below the surface (a cambic horizon) but without the clay accumulation or dark surface that would define other orders.

Aridisoles

Soil arid climate: water is lacking most of the year and the profile accumulates what the rain cannot wash away (carbonates, gypsum, salts) or clay from more humid times.

Ultisoles

Soil very washed out by a warm and humid climate, with a clay accumulation horizon and low base saturation: acidic and poor in calcium and magnesium.

Oxisoles

Soil extremely weathered tropical: there are almost no minerals left to provide nutrients and the clay is of low activity, rich in iron and aluminum oxides.

Histosoles

Soil organic: peat or plant material accumulated where water does not allow it to decompose. More than half of the top profile is organic matter.

Espodosoles

Soil acidic with a cold and humid climate, with a horizon where humus, aluminum and iron washed from above accumulate (the spodic horizon).

Those marked 1975 are names from the taxonomy many maps were made with, which the current edition no longer uses. They are explained anyway, because that is what the map says.