Measuring is knowing. That is the philosophy that they follow at Dutch greenhouse company LEMA tomatoes. And not just to determine nutritional schedules, but also when it comes to water quality. Owner and production manager Rob Marrewijk: "Water is a crucial factor for a good production, but you can’t see what is happening in the water by eye. Measurements give us the insight we need to provide our crop with good, sufficient and clean water."

System approach
The starting point for LEMA tomaten is to keep the irrigation system and water as clean as possible. "Last year we had some problems with blockages in the corners of the greenhouse," Rob explains. "As a result, the plants there dried up and that costs production. Giving more water is not desirable, because then other plants get too wet. We cleaned the whole system and now we want to keep it clean. We also want to keep crazy roots out. So we looked at a system approach with Edwin Datthijn and Robert-Jan Veens."

According to Rob clean outlet water is the starting point. "By using a tarpaulin and copper fertilization with Proteck we keep our reservoir water clean. On a daily basis we also sluice the contents of the pipes to the waste water silos, before we start giving water. We also use Intra Hydrocare, a product based on hydrogen peroxide stabilized with silver. The benefit of Hydrocare is that in the correct dosage it keeps the pipes and the water clean even in the farthest corners. We see this in the measurements that we perform." Fertilization specialist Robert-Jan Veens regularly comes by to do these measurements. Robert-Jan: "I measure the amount of ATP, a measure of the number of living organisms in the water. The instrument gives the value within 10 seconds. On the basis of the value we determine whether the approach is right or should be adjusted." Rob also carries out measurements using test strips. "Every week I check how much Hydrocare comes out of the drippers. If the value falls below a certain level, I temporarily increase the dosage."
LEMA tomaten has now been at it for a few months, to satisfaction. "Because you are measuring, you know exactly what is happening and whether this is to your liking. Robert-Jan still regularly comes by for measurements, but if everything runs well this will be necessary less often. We can be confident that the plants get good, sufficient, clean water, allowing us to enjoy an optimal production!"
For more information:
Van Iperen
Gert-Jan Dillo

Tel. 0413-354105