Biotite weathering in peaty-podzolic gleyic soil under conditions of a model field experiment

Changes in biotite (fraction 1–5 μm) after exposure in the T2, H, Eih, and E horizons of peatypodzolic gleyic soil under conditions of a model field experiment were studied by X-ray diffraction. It was found that the main transformations of the biotite in all horizons included the degradation of its crystal lattice into regularly interstratified biotite-vermiculite and randomly interstratified biotite-smectite structures and vermiculite. The transformation intensity decreased down the profile simultaneously with a reduction in the content of organic matter, roots, and microbiota population and activity. Chloritized structures were also present among the biotite weathering products in the E horizon. The main identified products of biotite weathering formed in horizons Eih and E over a five-year period of the model experiment were detected in the clay and fine silt fractions of these horizons and in native peaty-podzolic gleyic soils. This suggests that vermiculite and soil chlorite in the soils studied are products of soil functioning. It follows from the results, with consideration for literature data, that the weathering of biotite results in the formation of a potassium-buffering system.