The crop rotation is around the corner, which entails removing old crops in greenhouses to make room for new plants. For many growers it is also the right time of the year to do all the cleaning and tidying up. During the rotation, the grower may have to deal with wastewater that is not an issue during the rest of the year. Here are some tips on how to deal with this wastewater responsibly.
Stop the crop's irrigation on time so that the substrate mats can dry up as much as possible.
Leachate of crops
Leachate is the water that is released by crops. It occurs when the old crops are brought outside and are temporarily stored. This water should not be discharged to the surface, but to the sewer. If there is no sewer, an alternative solution can be found to take it to one over land. It is in any case advisable to allow the crops to dry up as much as possible before they are taken outside and to have them collected as quickly as possible.
Drain water substrate mats
This water may contain fertilisers and pesticides and should not be discharged to the surface. The water may be discharged to the sewer if one is accessible. At the end of the growing season, the crops should be allowed to absorb as much water as possible from the mats, thereby preventing leakage.
Cleaning water inside the greenhouse
If only water is used to clean the greenhouse, it is not a problem, but if cleaning products are added to the water, this water must be collected and discharged to the sewer.
To be able to give the new crop a clean start, the dirty water silos etc. must also be cleaned during crop rotation. This water contains fertilisers and pesticides and it should thus not be discharged to the surface, but into the sewer system.
Start new cultivation
The substrate mats are often cut to remove excess water. Since this water contains fertilisers and pesticides, it should not be discharged to the surface. To prevent all water from being drained at the same time and released to a too small sewage system, it is advised to first cut a small part of the film a later the rest. This allows for a gradual release of the water and makes it easier to capture and reuse the drainage water.
Drain water in the beginning of the cultivation
Many companies choose not to absorb the drain water during the first stages after planting, but to dispose of it. One argument for this is that new rockwool slabs contain substances that are harmful to young plants. Experience has shown that treating the drain water immediately after planting does not entail any additional risks to the plant.
Source: Omgevingsdienst Haaglanden
More information about water management in greenhouses: www.agrarischwaterbeheer.nl and