Slow-release fertilizer and preparation method thereof

The invention discloses a slow-release fertilizer as well as a preparation method and use method thereof. The slow-release fertilizer is prepared from the following components in percentage by mass based on that the total mass is 100%: 10-30% of nitrogen elements, 8-30% of phosphorus elements, 5-25% of potassium elements, 0.1-15% of a nanometer synergist and 0-40% of auxiliary materials, wherein the nanometer synergist is nanometer bentonite. The preparation method comprises the step of performing nanocrystallization treatment on the bentonite firstly and the step of performing mixing treatment on the nanometer bentonite and the other components. The slow-release fertilizer disclosed by the invention can strengthen the adsorption capacity for major elements such as nitrogen, phosphorus and potassium, reduce a leaching loss rate, effectively prolong fertilizer effects, and increase the utilization rate of the fertilizer. In addition, medium and trace elements of silicon, magnesium, iron, calcium and the like c