The generally salient qualities of the Pampean soil are richness in humus, deficiency in lime and good proportions of nitrogen and phosphoric acid. A characteristic feature of the subsoil is stratified layers of more or less calcareous concretions known as TOSCA (tufa or tophos stone). This layer is sometimes deep down; but in the southern region of the Province of Buenos Aires, beginning at Tandíl and Azul, it reaches nearly to the surface, so as to appear immediately under the soil, thus forming a waterproof subsoil impenetrable by roots.
The present writer has seen wheat growing on less than an inch of soil above the tosca; the roots spreading out at right angles to the stalks.
These layers of tosca or, in other parts, clay, are of great importance for holding water; seldom at any great distance from the surface.
On low and level plains when the soil is light or loose, chains of sand-hills are formed by the prevailing winds. Some of these are kept stationary by quick-growing vegetation, while others are constantly shifting. The shifting sandhill is, however, fast disappearing in consequence of the advances of pastoral industry; for, and by, which they are becoming fixed by herbaceous growth.
The tosca and clay subsoils have in many parts occasioned the formation of lagoons and swamps; the waters of which are, usually, at least brackish and often salt. A white or grey efflorescence seen in these swamps is locally called saltpetre, but in fact it only contains slight traces of nitre.
Towards the extreme North of the Province of Entre Rios and the Republic of Uruguay red soil heralds one’s approach to subtropical or tropical vegetation.
General Mitre, in his _History of Belgrano_, has said of the River Plate Territories:—
The natural pastures invited the inhabitants to the pastoral industry. The vast littoral placed the country in contact with the rest of the world by means of fluvial and maritime navigation. Its salubrious and temperate climate rendered life more pleasant and work more reproductive. It was indeed a territory prepared for live-stock breeding, constituted for commercial prosperity, and predestined by acclimatization to be peopled by all the races of the earth. Thus we see that the profitable occupation of its soil commences to be realized by means of live stock brought overland from Peru and from Brazil; that the commercial currents of the interior converge little by little towards the River Plate; that abundance and well-being are spread by this means; and that the first external act of the colonists after the foundation of Buenos Aires in 1580 is the exportation of a shipload of the fruits of their own work (hides and sugar), which awakens immigration and the commerce of importation.