The NVWA has designated new prohibited areas for irrigation with surface water. Existing areas have also been expanded. Only in Drenthe has one area shrunk. The designation of the Ketelmeer as a contaminated area in particular has consequences for farmers in Flevoland.
Every year the areas where a irrigation ban applies updated by the NVWA. For this year, the service has drawn the entire Ketelmeer, from the A6 to Overijssel. At first glance, this is not a problem, but that is not the case. In both the Flevopolder and Noordoostpolder, water is let in from this lake when there is a drought or to flush out draughts. Growers may soon be unknowingly irrigating with contaminated surface water.
Strict controls
This has no direct consequences for seed potato cultivation. After all, surface water may never be used for irrigation. A national ban applies to this. Danger lurks, especially when water mist is blown away or (accidentally) irrigated along with a piece of seed potatoes. Last season, the NVWA and NAK were already conducting strict checks on this.
Last year, the NVWA found four separate batches of seed potatoes with a brown rot infection. These batches all originated from seed potato companies in the Noordoostpolder. The infection was traced to the blowing over of surface water during summer storm Poly in July 2023. It is assumed that water washed over the dike and ended up on the potatoes. The four infected batches involve 22 different companies in seven provinces. Infected batches are destroyed. This also applies when there is a suspicion of infection. Infection can also have an effect on land use, due to a temporary cultivation ban.
More areas
The reason that the Ketelmeer has now been designated as a contaminated area is the brown rot bacteria found last year by the NVWA. The host plant bittersweet was previously found in a neighbouring watercourse. In addition to Flevoland, a new area has also been designated near Almen in Gelderland, which includes part of the Twentekanaal and the Berkel. In Overijssel, two existing areas have been expanded. This also applies to North Holland. In Drenthe, an existing area south of Emmen has shrunk.
The crux of the matter for farmers in Flevoland is when water is let in from the Ketelmeer. The NVWA does not check for this and does not issue any warnings either. The water quality in the north of the Flevopolder is a challenge for farmers in the area. Many sources are struggling with too high an EC content. That is why relatively much surface water is irrigated, which generally contains less salt. However, this spring the water quality is not equally good for irrigation everywhere.