To address the excessive headland space occupation and pronounced vehicle body roll caused by traditional U-shaped turning paths during plant protection sprayer operations in soybean–maize intercropping systems, particularly in fragmented and irregular plots, this study proposes a two-way operation scheme for unmanned sprayers. An improved Reeds–Shepp (RS) curve-based hybrid coverage path planning (CCPP) method is developed to optimize headland turning in non-perpendicular boundary scenarios and generate full-coverage paths for irregular fields. Simulation and field experiments conducted on four plots with an average area of 0.42 had demonstrated that, compared with the conventional U-shaped path, the proposed method reduces the average reserved headland width by 35.21% and shortens the non-operational path length by 21.76%. Under the same path-tracking controller, the turning heading deviation and roll amplitude are reduced by 21.38% and 31.73%, respectively. The results indicate that the improved RS-based path planning method can effectively reduce headland space occupation and enhance the stability and operational efficiency of plant protection sprayers.