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A pot experiment was carried out under greenhouse conditions with canola plants growing in a mixture of quartz (as the filling materials), glauconitic shale, and silicate dissolving bacteria. During a period of 180 days, pots were irrigated with K (+K) or without K (−K). At the end of the growing period, plants were harvested and their K uptake determined by flame photometer following dry ash extraction. The clay-sized particles in each pot were studied by X-ray diffractometer. Vermiculization of glauconite occurred with both nutrient solutions. The intensity of the 14 Å peak in the treatment with silicate dissolving bacteria and K-free nutrient solution was higher than with the complete nutrient solution. Under the treatment with silicate dissolving bacteria and Kfree nutrient solution the 14/10 Å peak ratio was 7.58 and it was statistically different at 95 % level compared to the peaks of the other treatments. Weathering of mica by K release from mica interlayers and the formation of vermiculite were the major process occurring in the rhizosphere. The results of mineralogical studies are therefore in line with the findings of greenhouse experiment both confirming that the application of glauconite can be beneficial to plant mainly through K release from mineral weathering even in a single growth period.

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