PROPERTIES, SOME CRITERIA OF CLASSIFICATION AND GENESIS OF UPLAND FOREST PODZOLS IN RWANDA

In southwest Rwanda, upland forest soils developed on quartzites and m icaceous sandstones along steep slopes have sometimes the macromorphol ogical look of 'true' Podzols. An investigation of the micromorphologi cal, mineralogical and chemical properties, however, reveals only weak indications of illuviation of amorphous organic complexes, This proce ss of cheluviation seems to be secondary relative to biological activi ty, Fe precipitation and weathering. The concept that cheluviation is the dominant process in the formation of spodic horizons and spodic ma terials would exclude these soils for the class of Podzols. Definition s of spodic horizon and spodic materials proposed in international soi l classification systems, should give preference to macro- and micromo rphological properties over chemical properties, because the former ar e directly related to different genetic processes (biological activity , oxide-reduction) which also could be responsible for their formation .