Performance of urea coated with polyurethane as a fertilizer for Phaseolus vulgaris L.
ABSTRACT Due to its great global importance, bean crop requires large-scale production, making necessary the usage of fertilizers. Among them, urea stands out as one of the most important. However, significant losses of nitrogen are constantly observed through leaching, volatilization and denitrification. In order to circumvent this problem, several research groups have studied the coating of fertilizers with polymers, since, through them, it is possible to control the release of nutrients as well as their availability in the soil. In this context, the present work aim son coating urea granules by means of a simple mixture of diphenylmethane diisocyanate and polyol polyether. Five types of coatings have been produced by varying the proportions of the reactants. All samples were characterized by infrared spectroscopy and scanning electron microscopy. In addition, in vivo assays were performed with Phaseolus vulgaris L.. Infrared spectra confirmed the polymerization by formation of the urethane bond. The micrographs showed coating with a thickness of less than 30 μm. Controlled release urea tests in water have shown that the polymer coatings delay release of the urea by approximately 50% over a period of 200 min. The results of the in vivo tests, in turn, showed that the use of urea with coatings in the 60:40 and 50:50 mass proportions (diphenylmethane diisocyanate/polyol polyether) increased the dry mass content in 52 and 22 %, respectively. In this way, it can be concluded that it is possible to coat nitrogen fertilizers simply with efficiency, allowing the release of nutrients into the soil and making it more sustainable.