Abstract A slow-release fertilizer was developed by encapsulating KNO3 pellets with graphene oxide (GO) films. The material was then subjected to heat treatment, where adjacent GO sheets were soldered and reduced to reduced graphene oxide (re-GO) sheets by potassium. After the re-GO shell formed on KNO3 pellets, the slow-release characteristics of the fertilizer dramatically improved. The process of releasing fertilizer was prolonged to 8h in water. We believe that this new coating technology could hold great promise for the development of environmentally-benign controlled-release fertilizer for crop production.