The cultivation is over but the care continues

Now that the harvest has started, it is gradually becoming clear how the flag is hanging in the onions with the yield and the quality. Exceptions aside, Kees Jacobs finds it not entirely easy. "The sorting is often fine. And many onions still need intensive care for a while in storage."

"A lot has already been harvested in the meantime", Kees Jacobs begins. My advice is to harvest now as soon as the soil allows it, because the harvest moment for the most beautiful skin has already passed in most places." The positive expectation that the Syngenta advisor expressed last time based on contacts with trade and growers does not entirely come true on closer inspection. "I think that it will be disappointing across the board. In many places I see a fine sorting of the land. There are too many plots with a story, for example sowing too late due to precipitation or growth delay due to hail damage. And we simply did not have enough sun for good production. There are plots with good yields, for example in Flevoland and Drenthe, but even there they could have harvested 10 to 15 tons more if the season had gone normally."

Bacterial disease
Last year it was the fat necks that raised eyebrows during storage, this year Jacobs mainly sees problems with bacterial disease. "You see noticeably more infections than in other years. There is also wind damage here and there, resulting in broken pipes. These are ideal entry points. But bacterial disease is also spread by hares and other game." If growers find bacterial disease on their plot, good advice is expensive, says the cultivation advisor. "If the affected bulbs are already soft, you can get rid of them in the field with a loader with axial rollers. And if they end up in the shed, you will probably have to dry them for a long time and intensively." Onions affected by bacterial disease can be recognized by their brown color and faster ripening. At a later stage, they become soft and start to smell. Fusarium onions, which are still found here and there, can also be rolled out with the axial rollers.

The equipment of the onion loader can also affect the storage life of the onions in other ways, says the Syngenta employee. "I see quite a few plots that are quite overgrown with weeds. You don't want large clumps of green material in the shed because of the air resistance; a hedgehog belt can provide good services in that case. And the axial set I mentioned earlier knows what to do with the fat necks. Because there are still plenty of them, although it is less bad than last year."

Dry carefully
Once in the shed, the important drying phase begins. "I believe that you should always dry with the support of a hot air gun," says Jacobs. "Drying with only outside air is false economy. You simply need a temperature difference around the clock and that only works with the heater." Jacobs is an advocate of gradual drying with air of 20 to 22 degrees. "That is the most reliable method if you want to prevent water sheets," he believes. In order to be able to monitor the progress of the drying process properly, Jacobs also believes that an RH meter is essential. "You have to continue drying until the RH has dropped to a value of 60%. You can't estimate that with your wet thumb. It usually takes about two weeks before you have reached that value. And after that you have to keep a close eye on the RH meter. It is normal for the RH to slowly increase again, but if it goes substantially above 80, you have to correct it. And then you definitely have to add a heater because it is already October." Only when the batch has a stable RH of 80% for a longer period of time, is the time to start cooling. Jacobs: "If you maintain a cooling rate of 1,5 degrees per week, you will be able to keep up with the season and have the opportunity to dry again along the way if necessary."

How MH works
The last tip Jacobs wants to give concerns the quality of the MH spraying. "That probably wasn't equally successful everywhere due to accelerated death by downy mildew", Jacobs suspects. "If you put a sample of about fifty onions on moist potting soil in mid-November at 15 to 20 degrees, the onion will start to sprout after a few weeks if the MH hasn't worked properly. You can also do this with two trays of onions and then inspect the bottom of the bulbs of the first tray after a few weeks. The onion will always start to form roots first, so that will give you a first impression quickly."