As plant and animal debris falls to the ground, it is quickly decomposed because of the warmth and moisture there. Thus minerals are found mainly in the forest plants, not in the soil. When the plants are removed and cultivation attempted, the soils quickly lose fertility. Once exposed to the sun, these lateritic soils soon bake into a bricklike material that cannot be cultivated. These regions receive 75-100 cm or more of precipitation each year.
Enough water falls on the soil so that much of it passes down to the water table.
As it does so, it carries minerals with it. In the U.S., the soils east of the Appalachian Mountains tend to be of this sort. Calcium and other minerals are not carried below the reach of plant roots and so remain available for use. This keeps the pH and general fertility high. Except to the extent that minerals are lost when crops are removed, the minerals simply recycle from subsoil to topsoil and back to the subsoil.