In many regions, and certainly on clay and loamy soils, the onions are sparse. This requires extra attention in the continuation of the cultivation and sometimes also a changed course or drastic decision. But first, Kees Jacobs and Michiel van Mol will discuss the lessons of the spring of 2022.
"I estimate that at least half of the plots do not reach the 600.000 plants per hectare", Kees Jacobs, onion expert at Syngenta Seeds, begins his story. "Although then you do not have to reseed, but it does indicate how serious the situation is." Over the past few weeks, Jacobs and his colleague Michiel van Mol saw that the onions were not doing well in many places. "The problems are greatest in the Noordoostpolder", Jacobs says. "We already have the first overseeding customers there."
In general, according to the cultivation experts, you can say that the condition of the onions leaves a lot to be desired, especially on the clay and loam plots. "The only exception is the southwest," Van Mol reports. "The onions are in reasonable shape there. On the sandy soils the onions are in better condition. Logically, they suffer less from crust formation, the main cause of the emergence problems on the clay. But the onions do not have it easy on the northeastern light soils either. is due to low temperatures. In any case, the onion experts have never come across a plot where the onions are 'like hair on a dog'.
Attention to seedbed preparation
In addition to the crusting caused by the torrential rains in early April and the strongly drying northeasterly wind that followed, there are other reasons for the moderate state, according to the onion experts at Syngenta Seeds. Van Mol: "That wind also brought cold, so that the seedlings stood still. But once an onion has sprouted, the plant must be able to stand up within a few days, otherwise it will collapse." This spring, the advantage of primed seed was therefore reserved for plots without crust or where irrigation was carried out on time.
Jacobs also points out the importance of correct seedbed preparation. "I see that driven implements are being used more and more often. This makes it easy to work too deep and that increases the chance that the seed will lie dry. With a fast harrow it is easier to work shallowly. The disadvantage is that you often have to take a little longer wait until the soil is proficient."
A false seedbed worked out well for tillage this spring, Jacobs and Van Mol said. "The land is already flatter, so you can work shallower. And you already have a good connection to the subsoil. That was a big advantage this spring. But the effect on the weeds was often disappointing, because the low temperatures not many weeds."
Irrigate or sow
Many growers with a mediocre position doubt whether they should overseed, Jacobs and Van Mol note in their consultancy practice. "As far as we are concerned, the limit for overseeding is less than fifty plants per square metre," says Jacobs. "If you are not too far below that and you can still find viable seedlings or dry seeds under the crust, then irrigation can be an option. Rolling or harrowing is no longer effective at this stage or does damage." Irrigation is very precise, adds Van Mol. "Give a small dose of no more than 10 millimeters and use a fine nozzle. And don't irrigate in strong winds, because then watering can also have the opposite effect."
According to the onion experts, overseeding until about 5 May can still produce a fully-fledged and fully-grown crop. "The relevant growers therefore have to make the decision quickly. Because they also have to order seed and perhaps call in the contractor." The recipe for overseeding tillage is simple: "Shallow tilling and deep sowing", says Jacobs. "And pick an early or mid-late variety."
Adjustment of cultivation technique or sales target
On plots with a thin or uneven stand, it may be necessary to adjust the cultivation technique. "If you're missing 20% to 25% of the plants, so with sixty plants per square meter or less, you have to lower your nitrogen dose," advises Jacobs. "So be careful with the second dose, because too much nitrogen results in looser onions. The potash yield can then also be reduced."
In addition, growers must be alert to the extra risks that an irregular stand entails. "It is becoming more difficult to determine the best moment for weed spraying. And you may have to adjust the mix of agents. You really have to be careful with the plants you have," says Van Mol. "The timing of the MH spraying is also becoming more difficult and the grower has to take into account a less good storage life. Not only because of the MH absorption, but also because of the greater chance of looser onions." In extreme cases, the grower must dare to consider a change in the sales target of an irregular plot. "Don't do that in July, but think about it now."
All things considered, the start of the 2022 season will touch the core of onion cultivation, according to the onion experts: "Onion cultivation has always required a lot of attention. And this year too, the grower will have to pay attention from start to finish."