Cultivation of Grafted Vegetables II. Development of Grafting Robots in Japan

Grafted seedlings are used commonly in commercial vegetable culture in countries such as Korea and Japan, where land use is intensive. Lee (1994) has reviewed the physiological aspects of grafting. The percentage of cultivated area of grafted seedlings in outdoor commercial vegetable culture amounts to 81% in Korea and 54% in Japan (Table 2 in Lee, 1994). In greenhouse cultivation, the percentage is higher in Japan (69%) and remains the same in Korea (81%). In particular, almost all watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] seedlings are grafted in both countries. Grafting is labor intensive. Farmers must manually graft numerous seedlings within a limited period. Neighboring farmers often graft seedlings in cooperation. An analysis of such group grafting showed that production of ≈3000 grafted cucumber seedlings required 6 h of labor from seven persons (Kobayashi, 1991). About 70% of the time was devoted to joining. As the average age of farmers increases, farmers’ demand for grafted seedlings increases. Several million grafted seedlings are produced by nurseries or by agricultural cooperatives every year in Japan. However, these organizations are also suffering from a labor shortage. Although the processes of filling trays with soil, seeding, watering, and controlling the growth environment are automated in some nurseries, grafting is done manually. Thus, developing automated grafting robots, which produce uniform seedlings at a lower cost, is a high priority. Much effort has been devoted to developing grafting robots in Japan, although none of them have yet come into practical use. This report describes four robots under development.