Soil order

Alfisol

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

What it means for farming

Acceptable fertility, but the surface layer is thinner and poor in organic matter. In the Pampas region many Alfisoles are sodic or floodable (Natracualfes) and are left for livestock.

Alfisoles on the maps

Udalf

Alfisol humid climate (udic moisture regime).

Ustalf

Alfisol from subhumid to semi-arid climate (ustic moisture regime).

Acualf

Alfisol with excess water: saturated near the surface part of the year, with redox depletions.

Xeralf

Alfisol with a Mediterranean climate (xeric moisture regime).

Boralf

Alfisol cold climate.

The definitions are a plain-language summary of the USDA Keys to Soil Taxonomy. The formal definition includes thickness, color and percentage thresholds that are left out here.

Sources