Soil sensors tell if tree needs water

If you can track the condition of the soil near your trees in real time, you can ensure ideal conditions. GreenDMS developed a soil sensor for this purpose. In an app, the tree manager can see what the tree needs at any time.

"In dry, hot summers, we see a lot of failure of young trees because they get too little or just structurally too much water," says Henk van Eldik, co-founder of GreenDMS. "We figured out that soil sensors could solve several problems at once. With that idea, we founded GreenDMS in 2021. In 2022-2023 we did pilots and now we are going to market with our basic sensor, which measures soil moisture, EC and soil temperature."

The sensor consists of a box to which a flex cable with measuring pins is attached. Van Eldik explains: "You place the box 10 to 15 cm below ground level, after which you stick the measuring pin in the place where you want to measure. Then you cover the whole thing with earth so that it is invisible and therefore not stolen or damaged. In addition to this basic sensor, we are also coming out with a sensor with three measuring points." The sensor transmits information to the GreenDMS portal six times a day - or more often or less often if desired. "The tree manager can see directly in the portal or in the accompanying app what the status of the soil is. He can use this information for aftercare (does the tree need water?) but also to learn from it how to design growing sites so that they are able to retain moisture." The correct interpretation of the moisture balance and corresponding watering advice is very important. "GreenDMS has made an important development in this, by linking the moisture percentages to the pF curve of the soil type in question. This allows us to give good advice". 

"The better the soil is arranged, the less water is needed," says Van Eldik. "So you can use water economically in times of scarcity. A big advantage is that you reduce your CO2 footprint when you don't have to unnecessarily pass by the trees with the watering unit and the tree doesn't have to downsize. With an optimal watering policy and a good growing site, trees no longer die from too much or too little water and the tree grows faster, fulfilling its functions sooner. Also, pruning can be reduced to a few percent at most. Because we also measure EC and soil temperature, we gain insight into the conductivity of the soil. This may prompt us to have a soil sample analysis done. In this way we advise the customer not only about water but also about the composition and mineral balance of the soil and how it can be improved. In doing so, we not only supply the technology but we are also consultants. From years of experience we know what is good and not good for the tree."

In addition to soil moisture, it is also possible to use other sensors to measure temperature in public spaces. "The well-known heat stress maps are often very generic, but do not always say anything about the actual temperature differences at specific locations. Our sensors can indicate local differences very precisely, with a view to municipal policy. You can see exactly what temperature drop trees bring about through their shading and air conditioning function, and which tree species are best for that." In addition to municipalities and project developers, the sensors can also be of interest to arborists, Van Eldik emphasizes, "You can use this to prevent sunburn in trees. We can measure how hot it gets in certain places and determine at what temperatures the bark of trees with thin bark will crack."

Van Eldik: "We focus on municipalities, contractors and project developers to prevent the loss of trees and to avoid unnecessary visits to water. And we focus on tree nurseries and fruit growers, because it gives them more control over the moisture levels and temperature in their plots. They could even control their irrigation system with this."