Rotary drilling type fruit tree precise fertilizer injection device and fertilizer injection method

The invention discloses a rotary drilling type fruit tree precise fertilizer injection device and a fertilizer injection method. The device comprises a fertilizer injection connecting frame (1) and an ultrasonic sensor (10) connected with a controller. A rotary drilling mechanism is mounted at the final-stage telescopic end of the multi-stage lifting mechanism on the fertilizer injection connecting frame (1); a fertilizer injection pipe (6) on the rotary drilling mechanism is communicated with a fertilizer liquid outlet (26) of the precise fertilizer preparation mechanism through a pipeline, and a fertilizer injection drill bit (7) is arranged at the bottom end of the fertilizer injection pipe (6); during fertilizer injection, the multi-stage lifting mechanism firstly drives the rotary drilling mechanism to linearly descend until a fertilizer injection drill bit (7) is in contact with the ground of a fertilizer injection point; then the multi-stage lifting mechanism continuously drives the rotary drilling mec