Recent research by Wageningen University & Research (WUR) on nitrogen leaching from consumption potatoes on sandy soil offers new leads in the debate surrounding the mandatory harvest date of this crop. Between 2018 and 2020, researchers in Valthermond looked at the leaching of nitrogen on sandy soil. According to advocate Vavi, the research offers new opportunities for the sector. The harvest deadline is a thorn in the side of potato processors and has a huge impact on the sector.
Just before the summer recess, a two-minute debate was planned on the subject, with three parties planning a motion on the mandatory harvest date on sandy and loess soil. That debate ultimately did not take place due to all the political developments in The Hague. The debate is now scheduled for the first week of September. The outcome of the debate could have a major impact.
New dates
The Ministry of Agriculture, Nature and Food Quality allowed WUR to stay at their test farm in Valthermond for three seasons taste grow potatoes for consumption on sandy soil and then sow a catch crop. Winter rye, winter barley and Japanese oats were examined as offspring. Experiments were also conducted with sowing dates between the end of September and the end of October and with two different nitrogen doses during potato cultivation. In short, three years of research shows that a direct relationship between harvest (and sowing date) and nitrogen leaching is not easy to establish. There are many factors that play a role in water quality.
"The report had a confidentiality period, but that has now expired, making the information available to everyone," says Vavi director Andries Middag. "Something has to be done in politics with these new insights. This also means that the officials involved must adjust their policy. It was previously based on research from thirty to 35 years ago. The new research looked at the relevant varieties Fontane and Agria. A lot has happened in three decades. The report shows that on average the growing season starts a week earlier and lasts two weeks longer. This also has an impact on what happens in the soil."
Two weeks longer
“The research puts many things into perspective,” he continues. The Commission of Experts on the Fertilizer Act (CDM) and civil servants have no choice but to look at the contents of the report. There are sufficient starting points to adjust the harvest deadline. There is now hard evidence that October 16 is also a good deadline. The Vavi advocates a date of November 1, but a new proposal is always better than the current October 1." Anyone who reads the report also sees that the relationship between nitrogen application and soil residue is difficult to establish and depends on many benefits. Does a nitrogen reduction in subsequent cultivation result in lower nitrate levels in the groundwater? That can be discussed.
If it is up to the advocate, then it is now up to politicians to take action. Afternoon: "There is no longer a coalition agreement that can hinder the VVD from passing a motion. VVD member Thom van Campen has previously spoken clearly about the measure. Other politicians from BBB, SGP, PVV and CDA, among others, have also expressed it about the measures. They must now keep their backs straight."