The invention belongs to the technical field of agricultural machines, and concretely relates to a deep soil fertilizer applicator. The deep soil fertilizer applicator comprises an earth cutting rod,a fixed frame, a limiting plate, planetary gears, an inner gear ring and cylinders, and the outer surface of the earth cutting rod is coaxially fixedly provided with a sleeve; the sleeve is rotatablymounted on the limit plate; the limiting plate is horizontally arranged above the fixed frame, the limiting plate is located below the rotary handle, and the limiting plate is connected with the fixedframe through the plurality of vertically-arranged cylinders; the number of planetary gears is four or more, and the planetary gears are engaged with a toothed structure of the sleeve; the inner gearring is rotatably mounted on the limiting plate, the inner gear ring is engaged with the planetary gears, and the inner gear ring is connected with and a through hole-through hole threaded structure;an inner cylinder is vertically arranged in the axial center position of a screw panel; and the inner cylinder is fixedly connected with the screw panel, the outer circumferential surface of a part,in contact with the inner cylinder, of the earth cutting rod is provided with sliding grooves, bosses are arranged on the inner wall of a second through hole of the inner cylinder, and the bosses arepositioned in the sliding grooves. The deep soil fertilizer applicator can realize smooth fertilization, and has a high working efficiency.