Peter Lemmen grows strawberries on both table tops and in greenhouses. Together with his cropadvisor Jan Janssen of Delphy, he tries to maximise the results from his cultivation. Peter has been using Growficient substate sensors since 2021 to optimise his irrigation strategy. Together, Peter and Jan talk about their approach.
Challenges: too wet substrate and red carrot rot
“We felt we were irrigating well,” says Jan, about the period before the sensors were purchased. So the shock was great when afterwards there was a wet layer at the bottom of the troughs, in which no roots could be found.
A consequence of the excessively wet substrate was red root rot, which caused the plants to lose their roots. Peter: “We tried all kinds of things to solve the problems. In the end, we mainly needed more insight into watering and substrate.” Cropadvisor Jan already had experience with Growficient’s substrate sensors. So after exploring several options, Peter and Jan started using the sensors in 2021.
More insight into the irrigation and the needs of the plant
Meanwhile, the irrigation strategy has changed a lot. The biggest reason? The insight Peter and Jan now have into the irrigation. “We went step by step,” Peter explains. For instance, they first determined the lower and upper limits, explains Jan: ”The idea was to see what we thought was the maximum. If we found the substrate optically at a certain level to be maximally wet, then we know the maximum.
On the other hand, we looked at what is as dry as possible and thus at what value you really need to irrigate to draw the lower limit there. Then you put the whole irrigation strategy under the microscope; how much water do I give and how does that affect the water content/sensor?”
“If we were used to start irrigating at 7.30 am, we could see in the dashboard that the plants didn’t become active until around 9pm. So you don’t have to start the irrigation immediately at 7.30 am, because the plant is not yet asking for water then.” In addition, Peter discovered that night shots are not invariably needed, according to the sensors. “It’s mainly about having much more insight and guidance now,” he says.
“And of course you have to keep walking around with green thumbs yourself,” thinks Jan. He says it helps to get a feel for the data by feeling the substrate here and there. “You also have to put in time and effort yourself.” Peter completely agrees: “It really is a process. You have to figure out for yourself what works best for your product and substrate, together with the insight provided by the sensors.” “Because you have much more insight, you dare more,” summarises Jan.
Meanwhile, Peter sometimes does not irrigate the plants for several days: “We have started growing much drier. I am sometimes amazed at how little water the plants appear to need.”
Jan explains that they discovered through the sensors that there were plenty of days in autumn when they didn’t need to water. “It was a risk, but we went further in this step by step, based on the insight from the sensors,” says Peter. This, of course, saves a lot of water. But as Jan rightly points out, “That’s nice, but ultimately a good cultivation is the most important thing”. Fortunately, the water saving then also makes for stronger roots. The harvest is good, and the failure rate has already been reduced by one to two per cent.
Saving on fertiliser and nutrients
Apart from water, nutrients can also be saved with the insights provided by Growficient. It is difficult to say exactly how much you save, as every year is different, Peter points out. “Last year, for example, it was extremely hot. But we do know that compared to other years, we are now saving 10 to 15 per cent calcium. And that even despite it being such an extreme year in terms of weather.”
Whether Peter could also save on potassium is hard to say. In the fruiting phase, on the contrary, you want overdrain, appoints Jan, and there should be as little stress on the fruit as possible. “Especially in that period, you shouldn’t want to make changes too much,” he says. Peter agrees: “You then run the risk of feeling it directly in your wallet”.
And it is precisely with that wallet that things are going well, due to the investment in the sensors. “I think I could earn back the Growficient system just on the fertiliser saved.”
One step further every cultivation
“If you get a better root system, it is much easier to keep better strawberries in the long run,” Peter says. As long as things are going well, Jan and he will continue on this path. And well it is going. “This is how we make the most of it step by step. Every cultivation we go one step further.” He says that from planting to picking, they have now found the optimum irrigation strategy. And that contributes to a good cultivation: “the most important thing”.
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