Soil subgroup

Haplustol tapto árgico

It has a buried clay horizon (argillic): an old soil was covered by newer sediments, and the current soil formed on top.

What the name says

Soil Taxonomy names are built from parts, and each part says something about the soil. From general to specific:

Taxonomic orderMolisolSoil 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.
SuborderUstolMolisol from subhumid to semi-arid climate (ustic moisture regime): water is enough in the growing season but there are long dry periods.
Great groupHaplustolWithin the Ustol suborder, it It is the simplest of the suborder: it does not have a clay horizon or any other feature that places it in a more specific group..
Subgrouptapto árgicoIt has a buried clay horizon (argillic): an old soil was covered by newer sediments, and the current soil formed on top.

What it means for farming

They are the soils agricultural lands par excellence: the Pampas grassland formed them and most of Argentine agriculture is done on them. They retain water and nutrients; its limitation, when there is one, is below: clay, sodium, calcareous hardpan or drainage.

The dominant agricultural soil of the semi-arid plain: western Pampas, southern Córdoba, northern La Pampa, the dry Chaco.

Most common surface texture
Loam
Most common drainage
Well drained
Typical effective depth
120 cm

Where it is found

According to the 1:500.000 national map, it covers about 112.708 ha, spread over 10 districts.

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National map units that list it. The scale is 1:500.000: good for seeing the region, not a single property.

ProvinceArea
Tucumán54.113 ha
Catamarca26.397 ha
Santiago del Estero20.712 ha
Córdoba8.837 ha
Salta2.650 ha

Districts where it is most common

It also appears on the detailed maps of: Buenos Aires, Santiago del Estero.

Other Haplustol subgroups

Soil series

Series are the specific soils, named after places, that detailed maps describe under this name. Two properties with the same series have the same soil.

Buenos Aires

Calderon

Soils it shares map units with

Several soils share each map unit. These are the ones most often found alongside this one: on a property, you will likely find them in the nearby low ground or on the next rise.

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