Steep and collapsed side slopes pose challenges for recovery planting. Spray planting using a remotely operated unmanned aerial vehicle (UAV) can serve as a safe and feasible solution for recovery planting under such circumstances. In this study, native seeds were molded into bullets and mounted onto a UAV to be precisely shot onto
side slopes with the assistance of the Global Positioning System and path planning. The proposed technology comprises
a spray mechanism, seed bullets, 40 bullet magazines, and a 100-psi air blast system to inject the seed bullets into the
side slope for germination. The seed bullets were composed of ecofriendly materials-including native species, local
soil, paper straws, and tooth sticks-all of which decompose naturally. The proposed innovative experimental plan comprises multiple stages-namely system planning, design and manufacture, site selection, spray planting tests, and recording and improvement-to establish a standard operation procedure for future application. The spray planting technique accomplished an attachment rate of 60% on side slopes steeper than 60%. After the monsoons and 2-3 months of germination, the planting site exhibited favorable preliminary results. Specifically, the germination rates of grass species were 37.5%, 58.5%, and 71% over two regions with areas of 20 m2 each. Furthermore, the germination coverage rates of tree species were 0.75, 2.1, and 2.84 saplings/m2 over a region covering an area of 55 m2. This study demonstrated a feasible and useful technology for effectively accomplishing recovery planting on steep side slopes.
Key Words: Spray planting, unmanned aerial vehicle application, seed bullet, soil catalyzing, injection mechanism.