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Aiming at the problems of easy injury to tree roots, low fertilizer utilization rate and uneven fertilization in orchard liquid fertilizer application, an air flow guided orchard fertilizer injection machine was developed to realize the mechanized application of orchard liquid fertilizer. A nested fertilizer injection device was designed for the air guided fertilizer injection method. The influence of the outlet hole parameters of the fertilizer injection device on the ventilation and fertilizer injection effect was studied by using Fluent fluid simulation software. It was determined that the number of vent holes and fertilizer injection holes was 4 and the diameter was 2mm. According to the actual operation of the fertilizer injection machine, the fertilizer injection gas-liquid pipeline and fertilizer injection down pressure device of the fertilizer injection machine were designed and analyzed. It was determined that the volume of the gas tank was 80L, the stroke of hydraulic cylinder was 450mm, the cylinder diameter was 40mm and the rod diameter was 28mm, which met the operation requirements. Through the interaction test of air flow guidance parameters and fertilizer injection parameters, the influence law of air flow guidance pressure and liquid fertilizer injection pressure on liquid fertilizer diffusion was explored. When the ventilation pressure was 0.8MPa and the fertilizer injection pressure was 1.5MPa, it was the optimal parameter combination. Based on virtual prototype technology, the modeling of air guided orchard fertilizer injection machine was completed, and the prototype was trial produced. Field tests were carried out in Yancheng, Jiangsu Province and Pinggu, Beijing. The field test results showed that the fertilizer injection machine had stable operation effect, and there was no liquid fertilizer overflow. The longitudinal diffusion range of liquid fertilizer was 264~320mm, the transverse diffusion range was 250~270mm, the operation efficiency was 0.10~0.12hm2/h, which met the operation requirements of liquid fertilizer in orchards.