Potassium Release from Biotite and Its Biological Weathering as Influenced by Organic Matter Treatments

In recent years, many studies have been carried out on the biological changes of micaeous minerals and their potassium release by plant types and microorganisms. However, there is little information on the effect of organic matter (OM) on the biological transformation of biotite and its potassium release. The objective of this study was to investigate the biological transformation of biotite and its potassium release influenced by organic matter treatments.A pot experiment was carried out in a completely randomized design with factorial combination and three replicates. Growth medium was a mixture of quartz sand, biotite and OM (0, 5 and 10 gr/kg cocopeat). During 120 days of alfalfa cultivation, plants were irrigated with either a complete or a K-free nutrient solution and distilled water as needed. At the end of the experiment, the dry matter of plants was determined and K uptake was measured by flame photometer, following dry ash extraction. Mica and its weathering products were separated from the quartz sand to analyze their clay fractions using X-ray diffraction (XRD). Under the K-free nutrient solution, an increase in plant dry matter and potassium concentration in shoot occurred in pots containing biotite and organic matter as compared to those with no organic matter amendment. Significant increase of plant K uptake occurred in pots containing biotite and organic matter, as compared to those without it, under both nutrient solutions treatments. XRD data showed the transformation of biotite under both nutrient solution treatments. Under complete nutrient solution, the addition of organic matter had a negligible effect on mineralogical transformation of biotite. However, under K-free nutrient solution, the addition of organic matter significantly increased the mineralogical changes.