Preparação e caracterização de quitosana incorporada com o fertilizante KH2PO4 como potencial aplicação na liberação modificada dos nutrientes NPK
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2020-02-21
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Universidade Estadual Paulista (Unesp)
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Os fertilizantes de liberação modificada têm conquistado âmbitos cada vez maiores nas pesquisas e em utilizações agrícolas devido a suas principais características de menores perdas de nutrientes e por seu menor custo, que envolve menos aplicações no campo e menores quantidades de fertilizantes utilizados, comparado aos fertilizantes convencionais. Este trabalho teve como objetivo elaborar fertilizantes com possível comportamento de liberação modificada, através da incorporação do fosfato de potássio monobásico (KH2PO4) no polímero quitosana, contribuindo, dessa forma, com as três fontes de nutrientes primários essenciais requeridos pelas plantas: nitrogênio, fósforo e potássio, por apenas dois recursos. Foram elaboradas duas amostras diferentes para posterior comparação, análise e aplicação. Os métodos utilizados no preparo das amostras foram: gotejamento em solução básica coagulante e casting. Foram feitas soluções de 8% de quitosana (m/v) dissolvidas em soluções de 5% de ácido acético, e subsequentemente foi adicionado o KH2PO4 (em diferentes concentrações para análise e para aplicação agrícola, foi usada a concentração de 60% (m/m) em relação à massa de quitosana). Foram feitas Microscopia eletrônica de varredura (MEV) para análise morfológica das amostras, Energia dispersiva de raios-X (EDX) para constatação dos elementos contidos nas amostras, o estudo da liberação dos nutrientes em solução aquosa (em pHs 5,4 e 6,7) e por fim, as amostras foram aplicadas em mudas de alface para efeito comparativo e de eficiência do material. Os resultados dos espectros de EDX apontaram que nas amostras feitas por casting, houve a incorporação do KH2PO4 no polímero, ao passo que nas amostras feitos por gotejamento foi acusado quantidades ínfimas de incorporação. As imagens de MEV indicaram que o método de preparação das amostras influencia diretamente na morfologia do material. Além disso, as amostras elaboradas por gotejamento alcalinizaram o pH da água e do solo onde estiveram em contato, prejudicando a liberação de NPK e o desenvolvimento das alfaces, inviabilizando a aplicação em campo. Por outro lado, as amostras feitas através do método casting, comportaram-se eficientemente, liberando os nutrientes em solução aquosa e permitindo o crescimento e desenvolvimento das alfaces, se comportando como um fertilizante promissor para aplicação.
Modified-release fertilizers have been increasingly used in research and in agricultural uses due to their main characteristics of lower nutrient losses and their lower cost, which involves fewer applications in the field and less quantities of utilized fertilizers, compared to the conventional ones. This work aimed to elaborate fertilizers with possible modified release behavior, through the incorporation of monobasic potassium phosphate (KH2PO4) in the chitosan polymer, thus contributing with the three sources of essential primary nutrients required by plants: nitrogen, phosphorus and potassium, from only two resources. Two different samples were prepared for later comparison, analysis and application. The methods used in preparing the samples were: dripping in a basic coagulant solution and casting. Solutions of 8% chitosan (w/v) were prepared dissolved in solutions of 5% acetic acid, and subsequently KH2PO4 was added (in different concentrations for analysis and for agricultural application, the concentration of 60% (w/w) in relation to the chitosan mass). Scanning electron microscopy (SEM) was performed for the morphological analysis of the samples, energy dispersive X ray (EDX) to verify the elements contained in the samples, the study of the release of nutrients in aqueous solution (at pH 5.4 and 6, 7) and finally, the samples were applied to lettuce seedlings for comparative effect and material efficiency. The results of the EDX spectra showed that in the samples made by casting, KH2PO4 was incorporated into the polymer, while in the samples made by dripping, tiny amounts of incorporation were accused. The SEM images indicated that the sample preparation method directly influences the material's morphology. In addition, the drip samples made the pH of the water and the soil where they were in contact alkaline, impairing the release of NPK and the development of lettuces, making the field application unfeasible. On the other hand, samples made using the casting method, behaved efficiently, releasing nutrients in aqueous solution and allowing the growth and development of lettuce, behaving as a promising fertilizer for application.
Modified-release fertilizers have been increasingly used in research and in agricultural uses due to their main characteristics of lower nutrient losses and their lower cost, which involves fewer applications in the field and less quantities of utilized fertilizers, compared to the conventional ones. This work aimed to elaborate fertilizers with possible modified release behavior, through the incorporation of monobasic potassium phosphate (KH2PO4) in the chitosan polymer, thus contributing with the three sources of essential primary nutrients required by plants: nitrogen, phosphorus and potassium, from only two resources. Two different samples were prepared for later comparison, analysis and application. The methods used in preparing the samples were: dripping in a basic coagulant solution and casting. Solutions of 8% chitosan (w/v) were prepared dissolved in solutions of 5% acetic acid, and subsequently KH2PO4 was added (in different concentrations for analysis and for agricultural application, the concentration of 60% (w/w) in relation to the chitosan mass). Scanning electron microscopy (SEM) was performed for the morphological analysis of the samples, energy dispersive X ray (EDX) to verify the elements contained in the samples, the study of the release of nutrients in aqueous solution (at pH 5.4 and 6, 7) and finally, the samples were applied to lettuce seedlings for comparative effect and material efficiency. The results of the EDX spectra showed that in the samples made by casting, KH2PO4 was incorporated into the polymer, while in the samples made by dripping, tiny amounts of incorporation were accused. The SEM images indicated that the sample preparation method directly influences the material's morphology. In addition, the drip samples made the pH of the water and the soil where they were in contact alkaline, impairing the release of NPK and the development of lettuces, making the field application unfeasible. On the other hand, samples made using the casting method, behaved efficiently, releasing nutrients in aqueous solution and allowing the growth and development of lettuce, behaving as a promising fertilizer for application.
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Fertilizantes, Liberação modificada, Biopolímero, Quitosana, Fertilizers, Controlled release, Biopolymer, Chitosan