In the arid climate of the tropics, there is, as well as the climate-type of soil, an intrazonal soil over Ca-rich mother rock, while in the plains there is a tendency for silicic acid rock soils to be formed. A high ground water level leads to the formation of amphi-percolative alkali soils, and finally in the pans exo-percolative salt soils form. All these soils show different profiles, different chemical reactions and different percolation direction. In the young state, they all have a basic reaction, which, however, can become acid in the endo-percolative types during the process of development, while this change only begins in the amphi-percolative alkali soils when degradation sets in. All these soils have very different values agriculturally, and they must therefore in any case be kept distinct and must not all be lumped together under the name of “alkali soils”.