Formation of soils with contrasting textures by translocation of clays rather than ferrolysis in flooded rice fields in Northeast Thailand

摘要: This paper describes the conditions for dispersion and flocculation of clays, impact this process on soils contrasting textures cropped with rice. Clay seems to be translocated down profiles along a topographic sequence. The clays are mixed kaolinite-smectite. cation exchange capacity these exceeds 20cmol c kg -1 . Both proportion smectite clay content increase increasing depth from top lower part pH ranges 5 8. aluminium oxide is small. soil solutions collected during rainy season were analysed Fe 2- major cations. We calculated sodium adsorption ratios (SAR) taking into account 2+ compared them critical coagulation concentration (CCC) found in previous study. contributed decrease SAR soils. comparison between SAR, total electrolyte concentrations CCC values showed that dispersible likely (i) disperse abandoned non-saline fields, (ii) flocculate saline uncropped as result large salt because either or content, (iii) flood water at surfaces fields under rain. No evidence ferrolysis was found. observed mineralogy can explained by translocation controlled salinity rice farming.