OBTENÇÃO E CARACTERIZAÇÃO DE MICROPARTÍCULAS DE ALGINATO PARA A LIBERAÇÃO CONTROLADA DO HERBICIDA TEBUTHIURON

Abstract

Herbicides currently employed in agriculture have several problems related to chemical stability, including: solubility, bioavailability, fotodegradation and sorption in soil, inherent in their physicochemical properties. Thus, the study of controlled release of herbicides is very important. In the present work we studied the controlled release of tebuthiuron herbicide (TBH) using alginate micro-particles containing different concentration of herbicide (4, 6 and 8 gL-1 ). The alginate microparticles were obtained by the dropping method and characterized by optical microscopy (OM), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX). The physical-chemical properties of the calcium alginate microparticles were obtained from by Ultraviolet–visible spectroscopy (UV-vis). The efficiency of calcium alginate microparticles containing TBH herbicide was evaluated for the control of bioindicators plants (lactuva sativa and cucumis sativus) in pre emergency condition. The assessment of phytotoxicity in the bioindicators plants were performed at 14, 21, 28 and 35 days after sowing (DAS). The mobility of TBH herbicide throughout the soil profile was determined by visual inspection and determination of dry matter. The controlled release mechanisms of calcium alginate micro-particles containing the TBH herbicide were explained by different mathematical models. The results shown that the polymeric micro-particles containing TBH herbicide were obtained successfully through a simple method. Based on the performed tests, it was found that the drip is suitable for the formation of alginate micro-particles formation. The alginate microparticles presented high encapsulation efficiency of TBH herbicide and are potential candidates for controlled release platforms in agricultural applications and can be effective for controlling weeds. The conventional herbicide registered mobility of 50 cm in depth, while the polymeric microparticles of 4 gL-1 exhibited a leaching by 20 cm in depth. In addition of presenting a significant result as the mobility in soil, the concentration of 4 gL-1 showed higher performance in control of bioindicators plants and enables a marked leaching ensuring the molecule efficiency and the lowest possible contamination.