Test figures: large variety of onion harvest, irrigation pays off

The harvest of the seed onions is almost complete. In the Boerenbusiness Dutch Crop tour Trial harvesting and measurements were carried out on the plots of the participating onion growers. Yields vary so widely this season that it is difficult to arrive at a common denominator. Irrigation seems to be rewarding this growing season, given the reasonable yields on plots that have had one or more applications.

Onion grower Arjen Jakobs from Wezup (Drenthe) is closing the onion growing season for the Gewastour by bringing in the last onions this week (week 41). Some of the plots of the other participants have been behind the shelves for several weeks or are already on transport g,gm in August. like the onions Oeffelt (North Brabant).

At the moment the onions had died or just before the harvest moment, trial lifting was done on the plot, whereby a square meter was lifted several times over the plot. These trial harvests were weighed, converted to yield per hectare and the size grading was determined. The plots in Ysselsteyn (Limburg) and Oeffelt (North Brabant) were sold ex-land. The tons on the delivery notes are included as net revenues in the table below. The onions from the other plots have been stored.

_{*Yield in tons of kilograms per hectare. 15% of the proceeds were deducted because of spraying tracks, headlands, lesser spots, etc.}

Growing season full of difficulties
The average hectare yield of the Gewastour onions is 53,6 tons net per hectare. That is more than 4 tons lower than the trial harvesting figures of season 2021. However, yields vary considerably from 85,9 tons to 34,0 tons per hectare, which is typical of the last growing season. Immediately after emergence it became clear that the onions on the sand in the south had an advantage over the rest of the Netherlands. Certainly in comparison with the loamy and clay soils, where many growers had a difficult turnout due to cold, drought and, last but not least, crust formation.

The latter was clearly present in many fields and resulted in a poor start to the season. So the first blow this season came early for some of the Dutch onion growers. Drought also took its toll not much later, although the heat didn't really hit until the summer months. Those two factors have cost a lot of kilos this growing season. The impact of the classic culprit downy mildew was limited due to the dry growing season.

Raining pays off this season
It was already the fourth relatively dry season in the last five years. Many onion growers have now gained extensive experience in irrigating the onion plots. On the plots of the Gewastour, this certainly seems to have paid off. The fields that have been irrigated do considerably better in terms of kilograms than fields that have not been irrigated. In some cases it was not possible to irrigate, such as the plot in Kortgene (Zeeland). From other dry years, especially in 2018, it has been learned that the moment of watering is very important and you should not wait too long. This season, many growers did not wait until the last minute until it was bone dry, but put the reel on the plot earlier to disrupt growth as little as possible.

As a result, there has been frequent irrigation, such as on the plot in Oeffelt. Grower Geert Jillssen has irrigated the plot a total of six times and with the right growing conditions there was 86,9 tons of one hectare. However, the yield in Oeffelt is not self-evident. This plot had a good yield, but Jilissen unfortunately had to oversow his onions with maize on another plot because it was growing so poorly. As mentioned before, the entire plot has been sold ex-land. 

The table clearly shows that the parcels that are not or hardly irrigated have the least kilograms per hectare. In the Gewastour, the sandy soil is also doing better this season. Of course, this does not apply to the whole of the Netherlands. In addition, the Gewastour Onions has 'only' 8 onion growers, which means that an outlier counts heavily and thus influences the average.

coarse
The Gewastour onions are relatively coarse at 66%. At the beginning of the season in April there was a heavy shower, which resulted in a crust on many fields. This resulted in lower plant numbers on several plots, leaving more room for the remaining onions to grow to the coarse size (60mm upwards). For example, a very coarse batch with no less than 90% from 60 mm upwards came from the plot in Eenrum (Groningen). Sampling was difficult on the plot due to the irregular position.

Robin Winter

Intern at the Boerenbusiness Dutch Crop tour

r.dewinter@boerenbusiness. Nl

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