To solve problems of non-adjustable fertilizer and low fertilization precision in the precision hole fertilization of dry direct-seeding rice, an adjustable socket-wheel precision hole fertilizer apparatus for rice was designed. The basic structure and working principle of the fertilizer apparatus were expounded, the structural parameters of key components were determined. The numerical simulation experiments based on the discrete element method were carried out by using sulfurized urea as the research object. Selecting the rotation speed of the socket-wheel, the length of the trough, the depth of the socket as the experimental factors, and taking the average amount of fertilizer discharging and the coefficient of variation of fertilization uniformity as evaluation indicators, the orthogonal rotation combined experiments with three factors and five levels were carried out. A multi-objective optimization method was used to determine the best parameter combination under the constraint of the target value of the hole fertilizer discharging of 1.500 g. The simulation results show that the coefficient of variation of fertilizer uniformity was the smallest and the coefficient of variation was 15.80% when the rotation speed of socket-wheel was 26.57 r/min, the length of the trough was 5.36 mm and the depth of socket was 5.64 mm. By using slow-release urea, sulfurized urea and bio-organic fertilizer as test materials, the bench test and field test was carried out on the fertilizer apparatus and the reliability of the simulation results and the adaptability of the fertilizer apparatus were verified.

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