Since the maturing process and the harvest method have a great influence on the quality of the products, they deserve special notice.
Principally, the transition to the sprouting resistance phase starts with maturity. This is the beginning of the transition to the second, generative year and serves for the overcoming of unfavourable weather periods.
The negative influence of physical disturbance factors on storage life demands that the majority of the harvest and preparation works have been finished when the sprouting resistance begins. The onion is then solid and dry, the neck narrowly and dryly constricted (as a protection against diseases).
The maturing phase is introduced by the cut off of the sap supply, especially upwards. The onion neck becomes soft, drops over, becomes shriveled and begins to “pull-in”. The most favourable time for the harvest is when aprox. 60% of the leafage has fallen down. To accelerate the drying process, the leafage is cut down on a neck length of 5 – 10 cm by leave cutters and the onions are immediately collected by disk and riddle chain diggers and arranged in the rows. Too long, dry leafage that remains on the bulb impedes the ventilation of the stocks, requires more laborius sorting, and not least, delays the drying process and thus prolongs the harvesting process.
When the weather is unfavourable and rainy, the natural drying in rows of the so-called one-phase harvest can be replaced by an artificial drying process, which, when handled correctly, nowadays leads to comparable results as the “ideal” drying on the field.
The onions remain in rows on the field or in the artifical drying installation, until the neck and the root are completely pulled in and constricted. Only when this process has been finished, the onions are taken to the long-time storehouse or prepared for the marketing. The choice of the harvest method depends on the factors soil and climate as well as on the variety (spring or autumn sown onions, regular maturing of the hybrids), on the existing machinery (harvest-, drying- and storage capacity) and on the marketing method (immediate sale, storehouse, central marketing) and must be determinded individually.
More-phase harvest, i. e. cutting off of the leafage, collecting and arrangement in rows, drying in the field, collecting and storing, is recommendable in warmer regions with relatively stable climate.
Single-phase harvest, i. e. immediate loading after collecting, artifical drying and storing or marketing is recommendable in regions with instable and rainy weather.
When the onions are put in rows on the field it is absolutely necessary that they are kept as dry as possible. This means that after rainfalls they should be turned over one or two times by riddle chain machines. When the weather is generally warm and dry, one or two rainfalls do no harm to the onions on the field. They may even destroy hard clods which otherwise would damage the bulbs during the loading and preparation process and, thus, make it necessary that the onions are sorted a second time.
For the placing in rows, and the loading on the cart or in boxes nowadays combiners, reconstructed potatoe diggers and other methods are used. The most careful method should be applied.
Height of fall and shocks by hard edges must be limited as far as possible by the corresponding measures such as catching bags and clothes, paddings etc. It goes without saying that onions that are damaged mechanically or by diseases mustn´t be put in the storehouse or on the market.