'Always looking for new insights into onion cultivation'

Arable farmer Peter Holster likes to experiment in onion cultivation. Growing on raised beds, testing with fertilizers and crop protection products. Soil scans and drone images are used for cultivation. All to ultimately grow a higher yield and, above all, better quality onions at his company in Marknesse.

The following will follow during the 2024 growing season Boerenbusiness Crop tour again 10 plots with onions. From planting to harvest, the participating arable farmers take us through the cultivation and decisions they make during the season. In this series of interviews we each get to know one grower, his company, vision and strategy. In this part onion grower Peter Holster from Marknesse (Flevoland). This is the second year that he is participating: "We have a very nice group of growers together and I have learned a lot through the many contacts with each other. It is valuable to be able to ask and advise each other where necessary, not only in cultivation terms, but also in terms of strategy and sales. Of course you sit in the entrepreneurial chair, but together you often achieve more," Holster begins.

After growing the Hypark variety for many years, Holster switched to the Hyway variety because of the strong properties of the variety and the well-developed root system. "We have a nice light sulfur soil for growing onions," says Holster. "The onions grow on a plot with a siltation rate of 20%, where potatoes were grown last year.

"I store my onions at home in a box store with mechanical cooling. This way I can manage my own stock and sell it gradually. In addition, I have invested in an extra cell for storage, which improves my strategic options. I am and remain convinced that a storage shed is not a hospital and the product does not improve. However, I think that thanks to modern techniques, such as good cooling and ventilation, a high-quality product can still be delivered."

Sowing technique
Holster uses primed onion seed on all his plots. Before sowing the beds, the beds are milled with a full field cultivator, so that the machine creates a package of approximately 15 centimeters of loose soil. The sowing is done by a contractor who uses a seeder with a kind of skis instead of wheels. These skis press a 'furrow' into the ground to place the seed in the ground and then cover it. This way, the seed is always in solid soil and with enough loose soil underneath, resulting in a sturdy root system.

Drones and Veris iScan
"I always focus on a thorough analysis of my plot for crop protection. I investigate the different soil conditions, ranging from heavier to lighter spots, and adjust my spraying accordingly. Using a Veris iScan soil scanner, I have mapped out my entire plot and I have detailed information about the organic matter content per 10 square meters. Holster says that he is also part of a drone worker group. "I also regularly scan my plots with a drone to assess the growth of my crops. This way I can determine where growth is strongest and where adjustments are needed. The scan provides insight into the soil, while I observe the crop itself with my drone."

Apply fertilizer in several stages
Holster's fertilization strategy has always focused on spreading several times during the year, instead of just once. "It is normally advised to apply nitrogen from 10 to 15 centimeters of crop height. However, my approach was different. Just as we eat several times a day instead of everything at once, I use the same principles for my onions. That is why I sprinkled something every week, which was a lot of work, but at the same time yielded good results. The crop grew nicely evenly, as I could see when cutting an onion," says Peter.

"This year I am participating in an Agrifirm trial with topcoat fertilization (a slow-release fertilizer), in which the nutrients are released slowly. I am conducting this trial on half of my plot to investigate whether my current fertilization method is sufficient or whether it use of topcoat is necessary. This allows me to determine whether I should continue to fertilize several times or whether I should apply one prior fertilization. We hope that this trial will give us more insight into the most effective fertilization strategy our onion cultivation".

"I enjoy doing tests anyway. In collaboration with BASF, for example, we have a test block with spray products, mainly focused on weed control. I learn a lot about how they deal with new, green products. The whole year round I watched and assessed that trial. Knowledge is power and at the same time I also enjoy exchanging knowledge with others. I like challenges, but I also like to have some certainty."

Challenges
According to Holster, controlling soil-borne diseases is a serious challenge within the agricultural sector, especially with regard to fusarium and weeds in onion cultivation. "The ban on certain crop protection products makes this even more difficult. Despite these obstacles, I remain positive about the future, because I work and believe in the importance of quality. Furthermore, we are faced with rising prices, which of course go hand in hand with our own increasing costs. Fortunately, it seems that we are slowly but surely on the right track, provided we achieve sufficient yield. In any case, I make sure that I sell my onions in a staggered manner It is no longer possible to find a buyer," Peter emphasizes.

As the world population continues to grow, so does the demand for food. “It is essential that politicians realize that food production is and remains vital to meet the needs of the world's population,” Holster ends.

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