Mineralogical changes in glauconite resulted from inoculation of silicate dissolving bacteria in the root zone of canola

Document Type : Research Paper

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Abstract

Microorganisms and rhizosphere can play a central role in the weathering of clay minerals. Mineral weathering is a major source of most essential nutrients including potassium. The objective of this study was to investigate the effect of silicate dissolving bacteria and canola rhizosphere on the transformation of glauconite. The experiment was carried out in a completely randomized design with factorial combination and three replicates. Culture medium was a mixture of quartz sand (as filling material) and K-bearing mineral (glauconitic shale). Canola inoculated with or without of silicate dissolving bacteria. Pots were irrigated with Stegner nutrient solution (+K and –K) during a period of 100 days. At the end of the experiment, canola shoots were harvested, and their potassium concentrations were determined using a flame photometer. The clay-sized particles in each pot were mineralogically studied using X-ray diffractometer. The results showed the vermiculization of glauconite occurred under both nutrient solutions. The intensity of the 14 Å peak in treatment with silicate dissolving bacteria and K-free nutrient solution was higher than complete nutrient solution. Under the treatment with silicate dissolving bacteria and K-free nutrient solution the 14/10 Å peak ratio was 7.58 and it was statistically significant at 5% level. Hence, The most significant change was the weathering of mica by K released from mica interlayers and the formation of vermiculite mineral. Mineralogical results were in line with the greenhouse experiment findings both showing the positive effect of the application of glauconitic shale even in a single growth period.

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