Caracterização físico-química e pré-avaliação agronômica de complexos derivados do glifosato e micronutrientes metálicos

Abstract

The association of phytosanitary products with metallic micronutrients from foliar fertilizers has been increasingly freguent for spraying crops aiming at the developmentof agricultura production systems. This practice is mainluy justified by the operational gain, reduction of application costs and optmization of agricultural spraying. With the objective of bringing improvements to this área of research, this work aimed at the síntesis and characterization of the herbicide glyfosate (H3Gly) with the micronutrients (Cu2+, Mn2+ and Zn2+), the preparation of formulations from these products and the evaluation of the agronomic effectiveness of potential prototype. The reactions between glyphosate and the metallic precursors CuSO4∙5H2O, MnSO4∙H2O e ZnSO4∙7H2O were carried out in 2:1 ratio (brinder:metal) in hydroalcoholic médium in the presence of a Strong base produced in colorless solids for manganese and zinc, and blue copper. The physical-chemical analyzes of the products resulting from the reactions received show that glyphosate is able to from chelates with the micronutrients Cu, Mn and Zn. The análisis by vibrational spectroscopy showed that there was displacement of characteristic bands of glyphosate after coordination, especially as bands related to vas(CO2) and vs(PO3), showing that there was a complexation with cases. With the analysis of the mass spectrum, by electrospray in positive mode, for the copper complex, it was possible to confirm the structural proposal for the molecule [Cu(H2gly)2] through the presence of the molecular ion m/z at 437.2356 attributed to [M+K]+ (calc. 437.9157), in addition to observing the fragmentation of the molecule through the loss of OH– fragments. Theoretical calculations were performed to better understand the mode of coordination of the ligand in the [Mn(H2gly)2] complex, where it was verified that the deprotonation of the carboxylic group forms the most stable species. The determination of the KPS of the complexes [Mn(H2gly)2], [Cu(H2gly)2] and [Zn(H2gly)2] showed that the former presented greater solubility in water. For the development of an applicable prototype, the built-in formulation model was adopted with the use of alkylpolyglucoside surfactant, obtaining a product with satisfactory stability containing the [Mn(H2gly)2] complex. The results of the agronomic pre-evaluation for the formulation prototype containing glyphosate complexed with manganese resulted in the maintenance of the herbicidal properties of glyphosate and, consequently, the productivity, in addition to showing a significant increase in the chlorophyll content and number of pods per plant of soy.