Abstract: With the continuous growth of China's orchard planting area and fruit output, orchard economy has become an important part of the agricultural economic system, and scientific and mechanized fertilization is the key to improving orchard management efficiency and fruit quality. However, the existing orchard organic fertilizer application machinery has prominent technical problems such as shallow fertilization depth, uneven fertilizer laying thickness, soil backflow after ditching occupying fertilization space, and asynchronous ditching and fertilization operations, which not only reduce the utilization rate of organic fertilizer, but also fail to meet the agronomic requirements of deep and narrow ditching for fruit tree root system fertilization. To solve these problems, a dual-row disc ditching and synchronous fertilization machine for orchard organic fertilizer was designed in this study, taking the goals of "deep and narrow ditching, clean soil throwing, and synchronous fertilization" as the core.The machine adopts a symmetrical single-disc cutter structure on both sides to realize dual-row deep ditching, which has the advantages of low energy consumption and high operation efficiency compared with traditional plow-type and chain-type ditching methods. It is matched with a rear-mounted auger fertilizer discharge device, and the fertilizer discharge pipeline is extended into the excavated trench to realize the seamless connection of ditching and fertilization operations, and can complete the synchronous ditching and fertilization operation with a depth of 600mm and a width of 200mm. Through the kinematic analysis of soil particle movement during ditching, the key parameters affecting the soil particle movement were determined, and the soil particle trajectory was optimized to ensure that the thrown soil falls outside the trench without backflow, reserving a clean operation space for synchronous fertilization. Theoretical analysis showed that when the disc cutter speed is 300～330r/min and the forward speed is 0.5～0.7m/s, the ditching and soil throwing effect is optimal without mutual interference, and the deep ditching operation effect is stable.A fertilizer accumulation analysis model of the fertilizer discharge device was constructed, and it was clarified that the rotation speed of the fertilizer discharge auger, the forward speed of the machine and the opening height of the fertilizer discharge pipeline are the core factors affecting the fertilizer laying thickness and uniformity. The discrete element software EDEM was used to build the simulation model of the fertilizer discharge device, the influence mechanism of each factor on the fertilizer discharge effect was analyzed through single-factor simulation experiments, and the orthogonal test was designed to optimize the parameter combination. The optimal operation parameters were obtained: the rotation speed of the fertilizer discharge auger is 30r/min, the forward speed of the machine is 0.6m/s, and the opening height of the fertilizer discharge pipeline is 45mm.Field tests of synchronous ditching and fertilization operations were carried out in November 2025 in the test base of Shandong Weifang Hailin Machinery Co., Ltd. The test results showed that the average fertilizer application thickness of the synchronous operation was 40～50mm, and the coefficient of variation of fertilizer application thickness was 5～10%, indicating good uniformity of fertilizer distribution; the stability coefficient of ditching depth and the consistency coefficient of trench bottom width on both left and right sides reached 90～95%, which fully met the agronomic requirements of deep and narrow ditching with synchronous fertilization. The research results solve the technical bottlenecks of the existing orchard organic fertilizer application machinery, and the design idea and parameter optimization method can provide important theoretical reference and technical support for the research and development and improvement of other orchard fertilization machinery, and have important practical significance for promoting the development of orchard mechanization and intelligent management.