Desenvolvimento e aplicação de fertilizantes de liberação lenta por biopolímero de quitosana modificado

Abstract

The rapid population growth associated with high losses of urea in the soil-plantatmosphere system, makes it necessary to develop new technologies to increase food production and improve soil fertility. Thus, this work aimed to produce ureabased Slow Release fertilizers, using water hyacinth (biomass), montmorillonite, humic substances and chitosan, using water rich in Natural Organic Matter (MON) as a solvent. The fertilizers were evaluated by absorption spectroscopy in the infrared with Fourier transform (FTIR) and the spectra demonstrated possible interactions between the components, indicating the possible formation of the proposed materials. Elemental analysis (CHN) of fertilizers, FERT1 (urea, water hyacinth, chitosan and water rich in MON) and FERT2 (urea, water hyacinth, chitosan, montmorillonite and water rich in MON) showed that the materials have good nitrogen content, 20% and 49% respectively, for application on soil. Scanning electron microscopy (SEM) showed that FERT1 and FERT2 have a spherical shape and surfaces with cavities, which can be used for nitrogen release, when associated with energy dispersion spectroscopy (SEM-EDS), it was observed that the surface of the FERT1 is composed of KCl, which can be considered a binary fertilizer, as it contains nitrogen and potassium in its composition. The swelling tests demonstrated that the FERT1 has a degree of expansion of approximately 200% in the pH range analyzed (5.5-7.5) and the water hyacinth reticulant, used in the synthesis, proved to be efficient, giving the material a lower capacity of water permeability, when compared to the spheres of urea, chitosan and humic substances (UQSH), produced without the crosslinker. A calibration curve was constructed using a UV-Vis spectrophotometer at a wavelength of 421 nm, for quantification of urea, obtaining a determination coefficient (R2 ) of 0.9999, confirming that the proposed method is efficient for determining said analyte. The leaching tests showed that FERT1 and FERT2 leached a very small concentration of ammonium (0.82 and 3.5 mg L-1 , respectively) in relation to the ammonium concentration leached by urea (43.1 mg L-1 ) and no nitrate leaching was observed for FERT1 and FERT2, while urea leached 13.1 mg L-1 of nitrate in 2 hours of experiment. In the water release tests, the FERT1 showed a maximum release after 30 days, unlike the urea that reached its maximum in just 2 days. Furthermore, FERT1 despite having a lower nitrogen content compared to FERT2, presented better characteristics and results for reducing nitrogen losses and minimizing environmental impacts.