Journal of the Indian Society of Soil Science

The chemical and mineralogical properties of five benchmark soils from Bangladesh have been studied. Free Fep3 content in these soils is low due to loss of iron along with the drainage water during the reduction phase. An accumulation of free Pep3 has been found to occur in the middle zone of the soil profiles which is possibly due to their fixation in the form of mottles. Free Fe₂O₃issignificantlycorrelatedwiththefree Mn0contentofthesoils. The SiO/

2

~03 molar ratios of these soils indicate the occurrence of non-uniformity in the soil parent materials. The SiO/RP3 molar ratio of the clay fraction implies that clay mineralogy is mixed with an abundance of 2: 1 layer lattice type minerals. Mica is the dominant mineral in the clay fraction of most of these soils. The content of smectite is high only in the Gangetic' alluvium soils. The other minerals in the clay fraction of these soils are kaolinite, vermiculite, chlorite and interstratified minerals. The clay minerals appear to be inherited from parent materials with very little in situ mineral transformation.