Large precipitation differences mark the 2025 growing season

The 2025 growing season will be characterized by large contrasts in precipitation. While the north of the country regularly received a refreshing shower, the south was a different story. Based on the data from the weather stations on the plots of the Boerenbusiness This year's crop tour also clearly reflects that image.

With the onion harvest finished and the potato harvest well underway, reports on yields vary widely across the country. This is largely due to the very uneven distribution of rainfall this year.

Every Crop Tour participant has an AgroExact weather station. It's interesting to see how much precipitation these stations recorded during the growing season, from March 1st to October 1st.

Precipitation Croptour plots potatoes

Precipitation Croptour plots onions

Water from irrigation has been filtered from this data.

Precipitation data from the Gewastour plots show significant regional variations in precipitation amounts. Above the major rivers, precipitation averaged between 350 and 400 millimeters in many cases. Below the major rivers, in provinces such as Zeeland, North Brabant, and South Holland, precipitation was generally limited to an average of around 250 millimeters. The difference between plots in IJzendijke (Zeeland) and Veelerveen (Groningen) was a staggering 231 millimeters!

Rain basis for good yield
The 2025 growing season demonstrates how significantly precipitation can impact potato and onion yields. On average, the net potato yield on the Gewastour plots is based on test harvests around 52 tonnes per hectare. However, there are significant differences by location: plots in northern clay regions yield significantly higher at 57 to 66 tons per hectare than plots in Zeeland and South Holland, where yields hover around 27 to 54 tons. Factors such as soil type and the frequency of irrigation play a role, but the data does show that precipitation from the air forms the basis for a good yield. Irrigation certainly helps a lot, but it never fully compensates for a lack of natural rainfall. Irrigation often occurs under less-than-ideal conditions: relative humidity is often low, and irrigation yields depend heavily on temperature, wind, and evaporation.

According to the test harvests, there are also onions large differences in yield between northern and southern growing areas. Fields in the north, such as Veelerveen, Kimswerd, and Marknesse, yield significantly higher at 67 to 86 tons per hectare than fields in Zeeland and Brabant, where yields range between 50 and 69 tons per hectare.

Precipitation deficit beneficial for 2026 growing season
The precipitation deficit in the southwest Netherlands has remained remarkably high since October 1st, especially compared to the eastern half of Groningen, where the deficit has now almost completely disappeared. There is a precipitation difference of approximately 400 millimeters between the two corners of the country. As winter approaches, many growers in the southwest Netherlands will no longer be so dissatisfied with this precipitation deficit. With the erratic weather we sometimes experience in the Netherlands, the accumulated dry buffer could actually contribute to a dry and easily workable soil structure towards next spring, a favorable start for the 2026 growing season.

Thus, 2025 confirms that regular, well-distributed rainfall is essential for a good yield. Natural rainfall not only ensures even growth but also prevents crop stress moments that are difficult to avoid with irrigation. Moreover, rain is often better distributed across the field than artificial irrigation. At the same time, this season demonstrates that irrigation, despite the large variations in rainfall amounts, remains valuable for limiting yield losses during dry periods. This is evident from the relatively small differences in yield figures, despite the large variation in natural rainfall between fields.

Note: less fanatic irrigation due to low potato prices
Regarding irrigation this season, we must note that due to the moderate or downright poor potato prices (which don't inspire much confidence for the storage season), several growers have been a little less diligent than they would otherwise have been in an expensive potato year. Especially in August, when crops were already well into their decline, an extra irrigation session might have helped yields. Several participants indicated that once the contracted yields were below target, they wanted to minimize additional costs.

Jan Willem Veldman

Jan Willem Veldman is an all-round arable farming editor at BoerenbusinessIn addition, he runs an arable farm in partnership with his father in Appingedam (Groningen), where, among other things, grains, onions and sugar beets are grown.

jw.veldman@dcami.com

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