About this Research Topic
Tropical and subtropical soils are, in a general sense, highly weathered. As a result, they are acidic, dystrophic and mineralogically poor. Weathering, many times associated with naturally poor parent material, has left these soils depleted not only of nutrients, but they lack chemically active secondary minerals. The situation is exacerbated by nutrient leaching and soil erosion caused by unsustainable agricultural practices.
In this context, the application of ground silicate rocks (or stonemeal), a technique known as remineralization, can be an alternative for soil amelioration. It is recognized that rock powders can be a source of plant nutrients, mainly by supplying P, K, Fe and Si, as well as trace nutrients to the plants. Rocks also have a capacity to raise the pH of the soil, acting as correctives of the acidity and releasing other nutrients, such as Ca and Mg.
Besides supplying nutrients, this low cost technology allows the so called remineralization process, that is, the recomposition of mineralogical soil, causing the formation of chemically active secondary minerals such as phyllosilicates of the smectite group, the 2:1 clays. The alteration of the mineralogy with the presence of these minerals results in the geological rejuvenation of the soil, with the increase of its cation exchange capacity (CEC) and of its fertility as a whole. Also, the addition of ground rocks that release Ca from silicates provides a way to capture atmospheric CO2, by producing pedogenic carbonate minerals.
The process of decomposition of the primary minerals from a ground rock, resulting in the release of nutrients and the formation of secondary minerals, depends on its granulometry and is mediated by the microbiota of the soil as well as by the plants. The action of microorganisms leads to the solubilization of rock minerals by two main mechanisms of action: acidification of the medium, by the production of organic acids that, through exchanges of binders, replace cations of the minerals with organic cations; and the production of chelants (siderophores) with high affinity for Fe and other elements and that destabilize the mineral. The growth of plant roots, in their turn, can produce a mechanical effect of rock disintegration, besides also release organic acids and siderophores, such as citrate, that will promote hydrolysis reactions and the complexation of elements derived from the rock minerals. Thus, the rhizospheric and mycorrhizal environments are fundamental for the transformation of ground rocks and soil recovery.
This Research Topic aims to showcase how plants and microbes interact to decompose rock minerals, with emphasis on genetic and biochemical aspects of the process. It will also cover carbonation in soils as a consequence of biological processes that form carbonate minerals. The fertility and mineralogy transformations in soil, as well as the effects in crop productivity as a result of the application of ground rocks are also within the scope of this Research Topic. We welcome all types of articles, including Original Research, Methods, Reviews, Mini-Reviews, Perspectives and thought-provoking Opinions.
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