Aerial Seeding

Aerial seeding is a logical extension of direct seeding. It can be useful where direct seeding must be applied to very large areas, for restoring steep, inaccessible sites, or where labour is in short supply. Many of the same species choices and pre-sowing seed treatments developed for direct seeding can be applied to aerial seeding equally well.
 
China leads the way with this technology; having carried out dozens of research programs on aerial seeding since the 1980’s and applied the method to millions of hectares, to establish plantations of mostly conifers and to reverse desertification. Since burying seeds, to prevent seed predation, is not an option with aerial seeding, the Forestry Research Institute of Guangdong Province developed “R8”, a chemical repellent to deter seed predators, whilst the Forestry Research Institute of Beipiao, Liaoning Province developed a “multi-purpose agent” which, in addition to repelling seed predators, also prevents seed desiccation, improves rooting and increases resistance of seedlings to diseases (Nuyun and Jingchun, 1995).
 
Previous aerial seeding for forestry in America and Australia (usually to establish monocultures of pines or eucalypts) involved dropping seeds from planes or helicopters, either unprotected or embedded in clay pellets (Hodgson et al., 1992). A more effective delivery system, for mixed native tree species, might consist of placing seeds in a biodegradable projectile, capable of penetrating the weed cover and lodging seeds in the soil surface. In addition to seeds, such projectiles could contain polymer gel (to prevent seed desiccation), slow release fertilizer pellets, predator-repellent chemicals and microbial inoculae (Nair and Babu, 1994) to maximize the potential for seed germination and seedling survival and easily growth. The use of an aerial drone, capable of accurately delivering up to 4 kg of seeds per flight using GPS technology, is currently being investigated. A drone offers low cost aerial delivery and monitoring options on a more frequent basis, including areas that are hard to reach by researchers.
 
One of the major obstacles to the success of aerial seeding on large, inaccessible sites is the lack of ability to carry out effective weeding, to protect the germinating seedlings from competition with herbs and grasses. Spraying herbicides from the air is routine in agriculture and could be used to initially clear restoration sites of weeds, provided there are few natural regenerants worth saving. However, after the tree seeds germinate, aerial herbicide sprays would kill the tree seedlings along with the weeds. Specific herbicides are needed, which kill weeds without killing either natural regenerants or seedlings germinating for seeds delivered to the site by aircraft.