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Existing rapeseed cultivation in the midlower Yangtze River area in China, which is planted after the ricegrowing season with sticky soil and a large number of straw, has a persistent challenge that the traditional deep fertilization device of rapeseed combined seeder obsessed with straw entanglement and soil adhesion, highlighting a need for deep fertilization technology and equipment. The purpose was to design an active antiblockage and deep fertilization device for rapeseed combined seeder. Based on the principle of active scraping and preventing plugging, the center of movement curve of the fertilizer shovel contacting soil was determined as the center of the rotary cultivator axis and the shape of the movement curve was set as enveloping the trajectory of the end of rotary cultivator. According to the requirements of antiblocking function of deep fertilization device and the requirements of fertilizer particle movement, the key parameters and allowable range of the design of fertilizer shovel structure were determined, such as the diameter of arc at the lower end of transition section d1, the angle of arc at the center of entry section θ2 and the diameter of arc at the upper end of transition section d2. Taking the maximum instantaneous velocity of fertilizer outflow from the end of fertilizer shovel as the optimization objective, the key structural parameters of fertilizer shovel as design variables and its allowable scope as constraints, a mathematical model for optimum design of fertilizer shovel structure was established. Through the simulation analysis of the fertilization process by the discrete element method, the factors of the center angle of circular arc section of fertilizer shovel entering soil θ2, the diameter of the transition section d1, d2 were taken as test factors. With vz as the response index, a quadratic regression orthogonal rotational combination test was carried out to establish the objective function of the mathematical model. The optimum design parameters of the fertilizer shovel structure were obtained as follows: the arc center angle of the entry section θ.2 was 36°, the arc diameter of the upper end of the transition section d2 was 93mm, and the arc diameter of the lower end of the transition section d1 was 66mm. The field test results showed that the flatness of rear chamber of direct seeder with deep fertilizer applicator was 17.96~21.37mm, the adhesion weight of single fertilizer shovel was stable below 1.5kg, the mean of fertilization depth was 91.10mm, the qualified rate of fertilization depth was 93.33%, the rate of fertilization broken strip was 1.08%, and the machine passed well, which met the agronomic requirements of rape planting and fertilization in the ricerape rotation area. 