Soil order

Ultisol

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.

What it means for farming

Deep and well structured, but acidic and of low natural fertility. They are the soils reds of Misiones: grass, tea, forestry, and agriculture with liming and fertilization.

Ultisoles on the maps

Udult

Ultisol humid climate, well drained.

Acuult

Ultisol with excess water.

Humult

Ultisol with a lot of organic matter at depth.

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