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Growing onions with less water
In some regions of the Netherlands, fresh water is scarce. Think of Zeeland or areas where salinization occurs, such as parts of the Flevopolder. At the Rusthoeve in Colijnsplaat, a trial is currently underway in which the Van Iperen research team is investigating how biofilm can be used to grow seed onions with less water.
The inspiration for this research comes from Italy, where onions in greenhouses are sometimes already grown under biodegradable foil. In our trial we work with four objects: a flat field application and an application on ridges of 75 centimeters, both with and without foil.
Benefits of biofilm
The foil used is made of corn starch and is completely biodegradable. In practice, we see that the foil lets water through from above, but retains moisture at the bottom due to condensation. This has advantages: the moisture remains available for the crop for longer and less water needs to be given via the hoses.
The objects without foil are watered twice a week via hoses: once with fertilizers, once without. For the objects with bio-foil, fertigation is applied only once a week. Thanks to the foil, the weed pressure also remains low. Weeds only grow along the edges and in the holes. We only had to spray soil herbicides twice.
In addition, the foil ensures that the soil warms up faster in the spring, which can normally provide a growth advantage. So far, that difference in growth is not clearly visible, but that may still come at a later stage.
Last year as a first step
Last year, biofilm was also experimented with. At that time, the machine was not yet suitable for precise application. The holes in the film did not end up directly above the seeds, which resulted in low emergence. The onions that did emerge had hardly any competition and grew to a yield of no less than 130 tons per hectare.
This year the machine was ready for the flat field application. The holes in the foil are now pricked exactly above the seeds. For the application on ridges the holes were still made manually this season, which again resulted in a lower emergence. A similar system will have to be developed for this in the future.
Other fertigation tests
In addition to the biofilm trial, other methods are also being tested at Rusthoeve to optimize fertigation. For example, we are comparing flat-field applications and ridges of 50 and 75 centimeters. In one object, the fertilizers are distributed over five doses per week instead of once per week. We are also investigating the effect of hydrogen peroxide on the growth of onions.
Come and see the Onion Day
Are you curious about how these innovative applications look in practice? We cordially invite you to come and view the test fields during the Onion Day. Both the biofilm objects and the other fertigation tests can be seen there.
