The invention discloses a hole-forming controlled-release method of enveloped controlled-release fertilizers and a preparation method of the in-situ reaction film-forming and hole-forming type controlled-release fertilizers. The preparation method comprises the following steps: adding different types of hole-forming materials into vegetable-oil
polyol, preparing to obtain a
coating material of the vegetable-oil
polyol containing a hole forming agent, by adopting two types of materials such as the vegetable-oil
polyol containing the hole forming agent and polyisocyanate as skeleton materials, spraying the two types of materials onto the surfaces of the fertilizers in a
fluidized bed by an in-situ reaction film-forming technology, carrying out in-site reaction, thus forming a
coating film and preparing the in-situ reaction film-forming and hole-forming type controlled-release fertilizers. The preparation method disclosed by the invention has the advantages that the permeability of the
coating layer of the fertilizers can be controlled, the hole-
diameter size, the
porosity, the
moisture permeability and the water
absorption rate and the like on the thin-film layer can be changed and the purpose of controlling the
nutrient release can be realized; the hole forming agent has no influence on the coating integrity of the controlled-release fertilizers, the
nutrient release mode of the coated controlled-release fertilizers can be changed, and the
fertilizer effect period of the coated fertilizers can be shortened, so that the
nutrient release of the controlled-release fertilizers and the nutrient need for crops can be well combined.