Development of Semi-Automatic Transplanter for Dense Planting of Bare-Root Onion Seedlings

Transplanting bare-root onion seedlings is currently conducted manually under difficult conditions and requires 100 to 110 workers to plant 700-800 thousand stands per ha. The present study developed and evaluated a semi-automatic transplanter that meets the demands of farmers for a densely populated field. Each planter features a carrousel with cells that are manually fed by a worker. The carrousel then rotates to deliver seedlings one-by-one into a drop tube, where gravimetric force guides them into a groove by made by a trencher. The seedlings are established by press wheels which gather the soil around their roots. The curvature of the drop tube and angle of the press wheel were evaluated and the best options were selected based on the establishment of the bare-root seedlings and the ability to keep planter width to a minimum. The transplanter consisted of nine planter units installed on two parallel toolbars. The machine was tested on a 1000 m2 field and it was found that the planting rows can be set as closely as 17 cm apart without disturbing the planted seedlings of the front row. This allows the spacing between adjacent units on each toolbar to be 34 cm, which is sufficient for the operators to sit next to each other. This arrangement established a stand at 90% field capacity for 3000 m2 working for 8 h at a travel speed of 0.25 km/h. The operation required nine laborers to work the machine, one to fill the seedling boxes and one to replant the missed sections of rows. The transplanter was able to do the work of 11 manual worker days for a 3000 m2 area at the same stand density as that obtained manually while saving 63% in labor.