ESTUDO DA FORMULAÇÃO DOS FERTILIZANTES NITROGENADOS E FOSFATADOS CONSTITUÍDOS POR VERMICULITA EXPANDIDA MACRONUTRIENTES E COMPOSTOS POLIMÉRICOS: COMPREENSÃO DO COMPORTAMENTO DE LIBERAÇÃO LENTA DA UREIA E DO FÓSFORO

Abstract

Fertilizers are essential elements in agriculture because they enable better production, however, some climatic conditions cause problems related to soil leaching. The intense incidence of sunlight causes the volatilization of the fertilizer, and the rocky materials present in the cultivated region hinder the mobility of these nutrients. These and other variations cause a decrease in the effectiveness of these fertilizers, harming plant development. To combat these aggravating factors, research is being carried out to minimize these adversities. In this sense, this study developed a nitrogen fertilizer and a slow-release phosphate fertilizer, capable of resisting soil leaching and volatilization. The work consisted in starting a previous study using expanded vermiculite interspersed with different amounts of urea by the mechanochemical method and later adding a biodegradable polymeric coating consisting of sodium alginate and hydrolyzed collagen. After analyzing the values of the first study, a second more detailed study was optimized, using vermiculite with four different granulometries, which were intercalated with urea by the recrystallization method, acquiring the slow-release nitrogen fertilizer. In this study, the experiment was also carried out to obtain the phosphate fertilizer through monoammonium phosphate MAP, applying the dilution method. In these two experiments, rice flour and critical pectin were added as binders to obtain the most resistant granules and, later, the polymeric coating consisting of sodium alginate and hydrolyzed collagen was applied. To better understand the release mechanism of these fertilizers, zero-order, first-order, Higuchi, and Korsmeyer-Peppas mathematical models were used. For the preliminary study, the X-ray diffraction (XRD), infrared spectroscopy (FTIR) and thermogravimetric (TGA) techniques were used, and for the second study, the characterizations of XRD, FTIR, TGA, X-Ray Fluorescence Spectroscopy (EDXRF) and scanning electron microscopy (SEM). The values of slow release of the nitrogen fertilizer showed that for the preliminary test a release time of 210 hours was available and for the second experiment the nitrogen fertilizer reached a release time of 720 hours, reaching a release of 80,28% of urea. The phosphate fertilizer achieved a release time of 684 hours, reaching a release time of 77,7%. The pot tests carried out with the corn crop showed that the sample with higher amounts of fertilization (T3) of nitrogen and phosphate fertilizers provided a greater development of the plant in relation to the other tests with smaller amounts of these fertilizers (T1 and T2). These values from the second experiment prove that the binders and the polymeric coating helped to prolong the release time.