Rochagem e suas interações no ambiente solo: contribuições para aplicação em agroecossistemas sob manejo agroecológico

• Autor(a) principal: Carvalho, André Mundstock Xavier de
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1631
• topic: Rochagem; Adubação orgânica; Intemperismo; Stonemeal; Organic fertilization; Weathering; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

The search for a social, environmental and economically advantageous alternative to conventional sources of nutrients makes the research with silicate rocks for use in agriculture especially important. Additionally, the new appreciation of the use of silicate rocks is also linked to the need for the use of large amounts of waste quarries and the expansion of agroecological farming currents. The main limitation of this practice, however, is the slow solubilization of minerals, and therefore, the slow release of nutrients to the plants. Some studies have been conducted in simplified controlled environments, overlooking the effect of soil organisms, mycorrhizal fungi or plant on the availability of nutrients from the rocks. In this sense, the present study was aimed at evaluating the potential use of silicate rock powders (stonemeal) in agroecosystems from the perspective of agroecology. This study was also aimed at assessing the role of biological components of agroecosystems and some biogeochemical processes involved in the release of nutrients from rock powders. To this end, three experiments were designed. The first, based on participatory methodologies in the field, using gneiss powder associated or not with different organic fertilizers on beans crop. The second experiment, carried out in a greenhouse, looked at the role of plant, soil microbiota and mycorrhizal fungi in nutrients availability from gneiss, steatite, and charnockite powders in successive crops with corn. The third and last experiment examined the role of biogeochemical processes involved in weathering, such as CO2, organic acids, and soil microbiota on the availability of elements of basalt, gneiss, steatite, and charnockite powders, which were evaluated in an Oxisol incubated under laboratory conditions. In the field, despite the slow release of nutrients from gneiss, the stonemeal promoted the growth of plants, increased absorption of nutrients, and promoted desirable chemical changes to the soil. In general terms, however, the release of elements from gneiss was little affected by the organic fertilizer. In the greenhouse, the results indicated that the rocks did not restrict soil biological activity or the activity of mycorrhizal fungi. Although the biological activity was important for the weathering of minerals, this study showed that the plant was also able to act upon the release of elements from the rocks when compared with the joint presence of the plant with soil microorganisms or in mycorrhizal association. Furthermore, the data demonstrated the need for experiments with plant and not just with soil in order to better evaluate the potential availability of elements in stonemeal. Under laboratory conditions, even with a short incubation period, the gneiss, charnockite, steatite, and basalt powders showed potential for use as sources of nutrients and promoters of improvements in soil chemical properties. The release of nutrients from the rocks was also affected by biogeochemical processes. The highlights were the performances of CO2 on the release of Ca and Mg from steatite, CO2 and organic acids on the release of P from basalt, soil microbiota on the release of Fe and Zn from gneiss and CO2 on the release of Mn and Ni. These changes strongly suggest the importance of the soil biological components on the viability of stonemeal and can help in the selection of technologies to increase the speed of release of nutrients from silicate rocks.