After a growing season that did not go well everywhere, the seed onion harvest is expected to start in full force at the end of August. Kees Jacobs, onion expert at Syngenta Seeds, has a few useful tips for a crop-friendly harvest and a good start to storage. "The onions are now worth good money, so bring them safely to the finish line!"
"In the end it will be a fairly early harvest," Kees Jacobs notes. "I didn't expect that with all those late and often thin plots. They usually ripen later. But the August heat wave provided the final push. Almost all onion plots are now being ironed or have already been ironed. And in many regions. the main crop has already started."
Late calamities
Right into the last weeks of the growing season, Syngenta's onion expert has observed calamities that cause concern and thought. Jacobs: "The drought situation has turned out to be really catastrophic in parts of Zeeland. There, crops have become ready for emergency and many growers have to settle for about 30 tons per hectare." But problems have also been seen in areas where it is possible to irrigate the onions. "Late fusarium has been observed on many plots," says Jacobs. "In some places that is really becoming a problem. And pink root is also becoming more and more common. This disease actually belongs in warmer regions, but is now also occurring here. Both with fusarium and with pink root, the problems are worse on plots where something is being done. the hand is with the structure or where the onions are grown too intensively." Jacobs advises to harvest fusarium plots early and leave them for a little longer. "Then the affected onions will dry up and there is a greater chance that you will lose them when loading and storing."
After the grain harvest, Jacobs saw the problems with thrips increase. "The less vital crops were particularly affected by this," he says. "Fortunately, problems with downy mildew have largely been avoided thanks to the warm dry weather. However, the chances for leaf spot disease increase now that you have more dew nights. So the advice remains to continue with the disease control until two weeks before harvest. But keep the keep an eye on the security term of your resources."
Accurate harvesting
With the current market quotations, good money can be made with onions, which is why, according to Jacobs, it is all the more important that growers do everything they can to harvest the highest possible quality crop. "Some plots have already passed the stage, but harvesting at 50% green foliage simply produces the most beautiful onions," says the cultivation expert. "Forget those last few kilos and go for the advantage of a nice color and a firm skin. Don't fold the foliage too low, a fist thick above the last leaf split is best, and make sure that the harvest ash is really below the onions continues and therefore does not hit them. If there is too much 'violence', an onion can burst and this will cause problems in storage. That is why you must also limit the drop heights and the harvester must not drive too fast. The machine must calm the crop can handle, without forcing, otherwise you will get damage or spill."
Jacobs sees that some fields are irrigated before the harvest. "Don't," he warns. "You optimize the conditions for fungi. If moisture is really needed to be able to harvest damage-free, it is better to wait for natural precipitation and let the crop stand for a while. With natural precipitation you usually also have lower temperatures and therefore less chance of mold - and bacterial problems."
Sunscreen and swath drying
In determining the best harvest time, there is another factor that does not make the decision any easier. "I hear in the corridors that the trade fears problems due to sunburn", reports Jacobs. "That is caused by bright sunshine. The underground parts of freshly harvested onions are especially sensitive to this. If you expect bright sun around the harvest, it is a good idea to wait a while. Then the onion can evaporate a bit, and thus cool down, and there is still foliage covering."
Waiting to harvest is at odds with the options currently available for a few days of swath drying. Jacobs: "When the weather is safe, you can leave the onions in the swath for four or five days. Everything that nature dries away is included. But if you don't trust it, for example because of sunburn, you can also quickly store the onions."
Dry for a long time
Once sanded in, the important drying phase follows. "With a good drying regime, you can maintain and sometimes even improve the quality of the batch," says Jacobs. "I'm a big proponent of drying at moderate temperatures of 20 to 22 degrees. That's a good compromise to prevent problems with head rot and water skins. Have heaters ready to keep the air temperature up at night. But watch out that you "Don't dry too quickly. Because then there is a chance that the neck will constrict too quickly and you will lose your drainage channel for moisture. If you don't want to dry completely, you can play with the hatches, the number of fans or the speed."
Drying should continue until the RH in the heap has dropped to about 60%. "Good RH measurement is very important in onion storage," says Jacobs. "I always recommend buying a good RH meter. But if you do have to do without an RH measurement, there are still a few practical farm rules. The onions should rustle and you should no longer be able to roll your neck between your thumb and thumb. index finger. And keep a close eye on the temperature. It should not drop too quickly during drying because that is a sign that there is still a lot of moisture to evaporate." After drying, the onions can be cooled slowly. "A degree a week is a nice pace," says Jacobs. Then you are at 5 degrees around Sinterklaas. And the RH may also increase a bit to about 80%."
Grab your chance
Now that the onions are trading at a good price, the decision whether or not to sell is perhaps the most difficult at the moment. There are several sides to this consideration, says the onion expert. "Cultivation has become a lot more expensive in recent years, and certainly this year. Due to the rising prices for fertilizers, fuel and crop protection products, your cost price may be a third higher than two years ago. But there are no guarantees about the price. one or two months. I personally wouldn't let this beautiful moment of sale slip, even if only for a part of your proceeds. Grab your chance."