'We leave as little as possible to chance'

"In seed potato cultivation we leave as little as possible to chance", say Wilco and Romke Sijtsma from Pingjum (Friesland). That is why a large number of 'aids' are given during planting, including the biological agent Serenade. "Since we started working with it we have had almost no problems with scab."

"Yes, we still had last year's autumn in the back of our minds when we were harvesting the last plots. At that time, there was more rain every day than they had predicted. Fortunately, it stayed a bit drier than the forecasts indicated and we were able to get everything in nicely." 

Wilco Sijtsma says this during a tour of the sorting and storage warehouse. Together with his son Romke and Agrifirm advisor Freek Pereboom, he discusses the things that still need to be done outside (mid-October), such as weed control in winter wheat and the upcoming carrot harvest. In the background, mechanics are busy installing an optical sorting unit between the sorting installation. "An investment in the future," says Wilco about this. "This increases the sorting capacity and allows us to do even more with the same people."

Satisfaction prevails
Annually, the Sijtsma partnership grows over 100 hectares of seed potatoes (from mini tuber to PB4) for three trading houses. The range of varieties is therefore quite extensive with Fabula, Colomba, Camelia, Donata, Jelly, Milva and Isa as the best-known names.

When father and son look back on the past seed potato season, there is mainly satisfaction. "Despite a somewhat later start and a few spots with water damage, the yields are simply good. On average, we do reach 45 tons and the sorting is also considerably better than last year. All in all, we can't complain," says Wilco.

The company has also been able to control the high phytophthora pressure. According to Wilco, this is largely due to the wide spray paths that have been laid out in all seed potato plots for at least fifteen years. "They really paid off last season. As a result, we were able to drive with the field sprayer whenever necessary."

A blemish on the season
Romke continues by saying that they are using every opportunity to prevent the virus. For example, they are placing aphid netting over the mini-tubers, they are placing straw between the ridges (in first- and second-year stems) to keep aphids out of the crop and they are using a very strict spraying schedule with mineral oil and aphid killers. "All in all, that seems to work fine. Even with the most virus-sensitive varieties, we had zero reactions this year." The fact that there were a few unexpected setbacks in the follow-up inspection in the third-year stems (PB3) feels like a blemish on the season to him, especially since very little virus was found during selection. Pereboom emphasises that although there were no major peaks in aphid pressure last season, the starting situation for 2024 was not exactly favourable. More leaf roll was also found in the area again. "That makes it even clearer how elusive the aphid and virus matter is."

Serenade while planting
The partnership has been doing the planting 'all-in-one' for years, or: planting (in pre-formed ridges) and ridge building in one operation. "The advantage of this is that you don't have to root in the ridges again and that the seed potatoes stay in a nice, moist ridge", says Wilco about this.

During planting, a large number of 'aids' are also provided for a smooth start and the most undisturbed growth possible. In addition to ammonium polyphosphate, a soil wetting agent and a plant strengthener with silicon, the biological agent Serenade has also been added for about ten years to promote the skin quality. "Since we Serenade we have had almost no problems with scab. And that while we are growing on scab-sensitive soil. That says something about the power of the product," Wilco describes his experiences. According to Pereboom, these experiences also match the many tests that have been carried out with the product in recent years. "Although the results have been somewhat erratic in some seasons, we see that Serenade has a beneficial effect on the peel quality over the years. In fact, it only needs to be a very small plus to make the product profitable," he says.

According to Romke, no (or almost no) scab also makes sorting a lot easier and can also be sorted 'sharper'. "Certainly with the somewhat stricter HZPC standard, there is really something to be gained. If you take the extra premium of 2 to 4 cents per kilo, that easily saves €400 to €800 per hectare. Even if Serenade contributes just a little bit to that, it is already worth it."

At least 300 liters of water
Finally, when it comes to the practical application of Serenade, Pereboom has only one tip: use at least 300 litres of water. "Certainly when, as in this company, multiple agents are put in the tank together, you need more than enough water to keep everything in the solution and to prevent flocculation. There are no significant restrictions for Serenade itself. You can combine it with all agents and the soil temperature does not play a role in the effect of Serenade", he concludes.

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