Loss of soluble substances and colloids from the top layer of soil by percolating precipitation. The materials are carried downward and are generally redeposited in a lower layer. This transport results in a porous and open top layer and a dense, compact lower layer. In areas of extensive leaching, the remaining quartz and hydroxides of iron, manganese, and aluminum form laterite. In such areas rapid bacterial action results in the absence of humus in the soil, because fallen plant material is oxidized and the products are leached away.
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