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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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Abstract. Loess-paleosol sequences (LPSs) are essential records for reconstructing Quaternary paleoenvironments. No previous study has provided numerical chronologies of loess in Lower Franconia, southern Germany; their chronostratigraphic assumptions have relied mainly on German (pedo)stratigraphic schemes. In this study, we provide for the first time a chronology for LPSs in Lower Franconia based on optically stimulated luminescence (OSL) dating using quartz and a comparison of K-feldspar (63–100 µm) and the polymineral fraction (4–11 µm). Our results show that all obtained ages are in stratigraphic order, ranging from Holocene to late Pleistocene, and in general confirm the former stratigraphical interpretations. A good agreement of the obtained ages is observed between both feldspar grain size fractions; they also agree well with the quartz OSL ages up to ∼50 ka. However, a marked difference between the growth pattern of the dose response curves and consequently different saturation characteristics of fine and coarse grains is found. Even though in our samples the discrepancy in ages is not very significant, we suggest the use of coarse-grained K-feldspar whenever possible in order to not be confronted with unknowns such as the mineral composition of the polymineral fraction.