Chitosan/urea based controlled release systems for urea: structural and environmental aspects

Abstract

Slow-release systems have been proposed in agriculture to mitigate the environmental damage caused by nutrient losses during fertilization. This study evaluates the potential of chitosan as a biopolymer for the development of controlled-release urea systems aimed at achieving more efficient and sustainable agriculture. A Chitosan/TPP/Urea (3.5% w/v) system was synthesized through ionic gelation, achieving an encapsulation efficiency of 36.9 ± 3.1% and exhibiting a slow-release profile, with only 8.69% urea released after 120 minutes. This behavior confirms the formation of a dense polymeric matrix that delays nutrient diffusion. Potentiometric analysis revealed that chitosan concentration influences the protonation degree of amino groups and, consequently, the ionic crosslinking density with TPP. Compared with conventional urea fertilizers, the synthesized system improves nitrogen retention, reduces volatilization and leaching losses, and increases nitrogen use efficiency (NUE). From an environmental perspective, the proposed technology contributes to reducing the nitrogen footprint, promoting more resilient agricultural systems with lower ecological impact.