Saturday, 15 July 2006

The Assessment of Manure Application on Potential Mobility and Bioavailability of 137Cs in Tropical Soils.

Maria Angélica Wasserman1, Antonio Passos Portilho1, Aline G. Viana1, Flavia Bartoly1, Daniel.V. Pérez2, Ana C. Ferreira1, Valéria Argolo1, and Carlos Eduardo Menezes3. (1) Instituto de Radioproteção e Dosimetria /CNEN, Salvador Allende s /n°, Recreio, Rio de Janeiro, 22780-160, Brazil, (2) Centro Nacional de Pesquisa de Solos/EMBRAPA, R. Jardim Botânico, 1024, Jardim Botânico, Rio de Janeiro, 22460-000, Brazil, (3) Colégio Agrícola Nilo Peçanha, Universidade Federal Fluminense, R. José Breves, 500, Pinheiral, 27197000, Brazil

More than sixty percent of agricultural Brazilian soils present restrictions for some crops due to low nutrient content, low cation exchange capacity, low organic matter content and acidity. In these soils, manure has been one of agricultural practices spread out between subsistence cultures for improving, for low cost, the physical and chemical properties of tropical soils. This practice has been improved by the commercial expansion of organic agriculture, pointed out as one of the most suitable technologies for the sustainable agriculture. In this work the role of manure in the mobility and bioavailability of 137Cs in Brazilian soil was experimentally investigated applying an alternative sequential extraction protocol. Previous results of geochemical partition for Cs and Sr, using this protocol, were coherent with root uptake. Further, the procedure allowed to identify the main soil properties that modify (or not) the soil to plant transfer at medium term. In this study, representative soils of Tropical areas: acid soils, with low content of organic matter, low fertility, devoided of 2:1 clay mineral was selected. To evaluate 137Cs bioavailability radish plants (Raphanus sativus, L.) were cultivated in pots containing soils spiked with 137Cs. The soils received varying doses of manure: a dose recommended for radish (2 kg/m2); half of the recommended dose; twice the recommended dose and without manure addition. According to this experiment about 4Kg/m2 of manure was able to reduce 137Cs transfer to radish. The percent of 137Cs associated with the oxidizable phase proportionally increased with the manure dose. These results provided a better understanding of the processes influencing the behavior of Cs in some tropical soils. This information is valuable in order to evaluate if manure can be suggested as a countermeasure for Cs contamination for the studied soil type. A better knowledge of radionuclides behavior in tropical soil is a fundamental step to keep quality in soil and food production on such vulnerable areas.

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