Investigation on the interactions among urea and three major components of lignocellulose in the biomass-based slow-release urea.

It is the theoretical basis to clarify the interaction mechanisms among the three major components of lignocellulose and urea for the utilization of agricultural waste and developing eco-friendly slow-release fertilizers. In this study, individual- and multi-component slow-release urea formulations were prepared from lignocellulose model compounds via the physical blending method. By comparing their physicochemical properties and slow-release performance, it was revealed that the key mechanism underlying the interactions among the three major components and urea is the "supporting skeleton-dense filling-chemical crosslinking" triad. Specifically, the thermally stable cellulose is the basic supporting skeleton of the slow-release urea, while meltable hemicellulose and lignin strengthen linkages by filling pores and acting as the "binder". The unique hydrogen bonding network among cellulose, hemicellulose, and urea effectively reduces the initial release rate of urea and the higher reactivity of hemicellulose enables potential chemical interactions with urea. Particularly, the interactions among the three components and urea exhibit significant synergistic effects, effectively prolonging the urea release duration. Thus, the slow-release performance of biomass-based slow-release urea can be effectively regulated by adjusting the content of the three major components, which provides a novel idea for the development of low-cost slow-release fertilizers with excellent slow-release performance.