Granular, Slow-Release Fertilizer from Urea-formaldehyde, Ammonium Polyphosphate, and Amorphous Silica Gel: A New Strategy Using Cold Extrusion

A new granular, slow-release fertilizer prepared by a cold-extrusion strategy (GSRFEx) based on urea-formaldehyde (UF), ammonium polyphosphate (APP), and amorphous silica gel (ASG) was presented. Characterizations showed that there were strong hydrogen-bond interactions and good compatibility among UF, APP, and ASG in GSRFEx. The mechanical properties as well as the slow-release properties of GSRFEx were greatly enhanced after the addition of APP and ASG to UF. Rape pot experiments indicated that GSRFEx could improve N-use efficiency dramatically and thereby facilitate the growth of rape. Importantly, as an economical, effective, and environment-friendly technology, cold extrusion has great potential to be applied in horticulture and agriculture. We hope that our work can offer an alternative method for the design of slow-release fertilizers with desirable properties.