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. The use of controlled release fertilizers is a trend for improving productivity, reducing costs and environmental pollution. Such materials release gradually the nutrients to the plant in order to supply its requirement and are an alternative to improve fertilization. The preparation of a microsphere from natural materials (chitosan and montmorilonite clay) added with nutrients, according to the needs of plants nutritional, is one of the main motivations of this work. The addition of lamellar silicates as natural clays is a promising alternative to increase water and chemical compounds sorption capacity. In the present chitosan/montmorilonite clay composites were prepared via inversion phase and thermal, structural and morphologically studies were performed. The release of the KNO 3 was realized in water using conductimetry and time domain reflectometry technique was used to monitor the in situ release in soil. Double coated microspheres provide the better nutrient encapsulation and a swelling of 200% was observed. The release was influenced by pH and fast release was observed for pH 4 and 5.5. According to the soil tests a slow release was observed since the KNO 3 delivery was accompanied during 60 days showing higher values in the first ten days and a constant value until 60 days.

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Dedico este trabalho a Deus que permitiu que tudo pudesse ser realizado. AGRADECIMENTOSÀ minha orientadora Profa. Dra. Roselena Faez pela convivência e por compartilhar seu conhecimento contribuindo para meu crescimento científico e intelectual, bem como por todas as oportunidades proporcionadas durante minha trajetória no Laboratório de Materiais Poliméricos e Biossorventes. À Profa. Dra. You-Lo Hsieh por ter me recebido e supervisionado em seu laboratório durante meu estágio de pesquisa na Universidade da Califórnia, UC Davis, e pelas colaborações nos artigos científicos.