Method for preparing organic fertilizer

The invention discloses a method for preparing an organic fertilizer. The method sequentially comprises the following steps: grinding rape straws into small sections; mixing a rapid preservative agent, urea, plant ash and the ground rape straws in parts by weight: 1000 parts of rape straws, 1-8 parts of rapid preservative agent, 8-37 parts of urea and 70-150 parts of plant ash; adding the mixed materials which are uniformly mixed into a fermentation tank, fermenting for 15-20 days by adopting an aerobic fermentation mode, and controlling the carbon-nitrogen ratio to be (25-30):1 in the fermentation process; screening the thoroughly decomposed powder and granules after the fermentation is finished, stirring to be uniform in a stirrer, preparing granules in a granulator, drying in a drying machine, thereby obtaining the finished granules. The method is simple in overall process, convenient to implement and low in cost, the prepared organic fertilizer is high in fertilizer efficiency, the rape straws can be effectively utilized during application, and the problem of environmental pollution caused by incineration of the rape straws can be solved.