Encapsulation of nitrogen fertilizers in mixtures with organoclays for controlled release

To increase the effectiveness of fertilizers, new controlled release nitrogen fertilizers have been developed from a mixture of urea and natural smectitic clays and organoclays with different surfactants (ionic and nonionic) encapsulated in an insoluble, biodegradable polymer film. Smectitic clays were classified according to their chemical, physical and mineralogical aspects. Mixtures of urea and natural/organoclays were pressed, and the specimens were dipped into a polymeric solution of poly-e-caprolactone and acetone (solvent). The resulting controlled release fertilizers were analyzed by infrared spectroscopy and by scanning electron microscopy. The release of urea was evaluated by kinetic dissolution test in aqueous medium as determined by analysis on a UV–visible spectrophotometer. The results have shown that organoclays, especially those with nonionic surfactant coated with a PCL film, favored kinetic and gradual delay in the release of urea. This meets the standards established by the European Committee for Standardization, favoring, therefore, important agro-industrial advances at both national and international levels, securing sustainability in the technological sector.