Effect on N release by urea coating with chitosan, starch and urease inhibitor

Food production often relies on nitrogen fertilizers, which can harm the environment when dispersed in agroecosystems. A new urea coating additive, made from chitosan, starch, and N-(n-butyl) thiophosphoric triamide (a urease inhibitor), has been developed to mitigate these effects. The additive was tested for its impact on ammonium (NH₄) production and urea release in water, characterized using Fourier transform infrared spectroscopy (FTIR), and subjected to bioassays on lettuce and rocket. The additive decreased the urea release rate in water by 12 %, as predicted by the Korsmeyer and Peppas model, indicating Fickian diffusion controlled by concentration gradients. FTIR analysis revealed that the interaction between chitosan's amine groups and urea's hydroxyl groups slowed the release. In lettuce and rocket, the additive enhanced root development, increasing surface area by 97 %, root volume by 100 %, and thin and thick root growth by 65 % and 131 %, respectively. After 24 h, the fertilizer produced less ammonium when in contact with urease. The production cost of this fertilizer was only 20 % higher than conventional fertilizers, showing that applying NBPT, starch, and chitosan to urea can reduce waste and improve key aspects of sustainable food production.