Japanese onion harvesting machines save a huge amount of time and effort for the farmers of rural Japan. The machines automatically pull the individual plants from the ground, remove soil, cut away excess root material and present the stalks to the operators for neat bundling.
Non-bulbous straight onions (commonly known as “Japanese Onion”, or “Naga-negi” lit: long onion in Japanese) are a popularly farmed vegetable in Japan. We have written about this particular variety of onion in the past, so if you want more information about it’s farming and general use in Japan, please check our original post here.
Japanese onions are usually grown within mounded rows of soil approximately 3 feet apart and 1 foot high. The mounds are formed during the growing season, as a machine is used to partially bury the plants from the side to provide development of the desired long, white stalks below ground level. This growing arrangement is also suitable for providing access to the harvesting machines that straddle each row during harvest.
Skip to the bottom of this page to view a video of a typical onion harvesting machine in action.
Machine harvesting of Japanese onions requires at least two operators for efficient workflow. Many farms plots however, are owned by individual families, so harvesting tasks are shared amongst family members to reduce workloads and to get the crop to market more quickly.
Harvesting machines have an automated uprooting system towards the front of the machine and a bundling and cutting area at the back.
The first part of the uprooting section is equipped with angled guide wheels that run along either side of the deep onion rows. Along with the main rear tracks, these wheels help the machine stay on course as it moves.
A pair of small plough discs are used to cut through the sides of the mounds approximately 4-6 inches from the base of the onion stalks. This cuts away the bulk of the root mass that hold the plants tight in the ground. An additional hydraulically positioned ploughing apparatus also gently lifts the soil and cuts away roots from underneath the onion stalks as the machine moves forwards.
The next mechanism of the machine then firmly clasps the thick stalks between two spring loaded conveyor belts. The belts run from ground level up towards the operator at an angle of approximately 45 degrees. As the belts move, the onions are gently lifted out of the soil.
Once clear of the ground and in a vertical position, the lower root portion of the onion stalks are contacted by a rotating tiller-like mechanism. This knocks the main clumps of soil away from the roots. Any remaining longer roots then dangle over a rapidly rotating roller which is designed to tangle and rip away excess material. Only a 4-6 inch long portion of the original root structures remain after this process.
The conveyor continues to hold the onion stalks in a vertical position until it reaches the top of the slope, where the belts twist 90 degrees and then presents the stalks horizontally to the machine operator.
This operator, who also doubles as the harvester “driver”, batches the onions into bunches of approximately 30 stalks each. He places the stems atop a flexible straw matting, ensuring the white bases of the stems align neatly with the edge. The matting is then rolled to bundle the onions and is handed to the second operator working at the back of the machine.
The second operator ties the straw matting firmly around the bunched onions before separating a large portion of the green upper leaf tips with the swift, clean cut of a large machete.
While the discarded onion tips are usually edible, they are often slightly brown, bent or insect damaged. Japanese wholesale market standards require their removal. In later processing, further trimming will also occur to ensure all stalk lengths are totally uniform.
The discarded leaves are left on the ground and are later tilled back into the soil to return nutrient. This also discourages insects from laying eggs and breeding in the soil.
With the field activities of harvest complete, the bundles of onions are packed onto a small truck and transported back to a processing facility for sorting and further preparations before sale.
Some interesting techniques are used to prepare the onions for the high presentation standard demanded by Japanese supermarkets. We will cover the machines and techniques involved in that preparation in a separate post soon.
If a picture is worth a thousand words, a video is worth a million!
As we mentioned above, we have written about the farming of this particular variety of Japanese onion in the past, so if you want further information about it’s farming or use in Japan, check out our earlier Winter-time post here.