Release of potassium from rock powder by the yeast Torulaspora globosa

The alteration of minerals in rocks and the availability of elements for plant nutrition require long periods of time, and microorganisms are thought to induce the release of potassium and phosphate from rocks. In this context, this work evaluates the role of the yeast Torulaspora globosa, isolated from the sugar cane rhizosphere, in the solubilization of potassium from alkaline ultramafic rock powder. The experiments were performed in liquid medium, with or without agitation, at 30°C with the following treatments: culture medium + alkaline ultramafic; culture medium + yeast suspension; and culture medium + yeast suspension + alkaline ultramafic. The results showed that as much as 38% of the total potassium in the rock was released in the medium with the yeast during a 15-day period of incubation. Acid production may be the mechanism by which the yeast solubilizes potassium because the total acidity increased during the sampling period. Agitation (which increased oxygen availability) resulted in approximately 20% more biosolubilization of the alkaline ultramafic rock than with the static culture. These data indicate the potential for this yeast in biosolubilization processes and biofertilizer production

Biological activity in Cerrado soils: evaluation of vegetation, fire and seasonality effects using the “bait-lamina test”

Aims The Cerrado, a South American savanna, is con- sidered a priority for conservation. In this case study, we assessed soil feeding activity as a way to improve un- derstanding of the ecosystem functioning, in order to support and refine conservation strategies. Methods Soil feeding activity was assessed using the bait-lamina method under different environmental con- ditions: in the dry and rainy seasons, in burned and unburned areas, and under native and invasive grasses. Results Feeding activity was significantly reduced after fire, but recovered to pre-fire levels with the rains. Activity increased significantly during the rainy season in both areas, being more pronounced in the unburned area. The highest feeding activity was observed under the invasive grass (Melinis minutiflora). Feeding activ- ity declined with soil depth and was affected by season and fire. Conclusions Seasonality was the most important factor affecting the feeding activity of soil organisms, followed by the fire history and the extant vegetation. Although this method does not allowdistinguishing between feed- ing activity of different organisms, it can provide valu- able insights into differences in soil functioning due to changes in environmental conditions