Lichtsensoren op het agroforestryperceel

Digging Deeper: the sensors are on edge!

Through the 'Digging Deeper' series, you can follow the developments and results of Inagro's own agroforestry plot from the front row. In this edition, you can read about the past press event, the setting up of some sensors and other work on the plot. And although our first nut harvest is still a few years away, we also went to explore 'Nooly', a small and local start-up that collects and presses nuts for oil.

Research plot in the media!

West-Flanders deputy Bart Naeyaert planted the final walnut tree last month, officially kicking off this long-term research project. During a press event, the deputy emphasized the potential of agroforestry as a production model with focus on soil, water and biodiversity. "Farmers need practical experience and good examples. With this new plot, we want to conduct our own research on the potential of agroforestry on one hand and introduce farmers to it through demonstrations on the other hand. This way, we can inspire farmers and inform and guide them better in the future," the deputy said. He cited the cooperation with local farmers on this new research plot as a great asset!

Agroforestry groepsfoto aanplant

Placing sensors: an overview

What is the impact of trees on soil and cultivation? How do they change the microclimate in the plot? How far into the plot does that effect extend? These are some of the research questions we want to answer and substantiate scientifically. That’s why we placed a lot of sensors on our plot last month. These will take measurements all year round. Below is an overview of the sensors we installed.

1. Soil moisture sensors

By applying organic matter, trees increase the storage capacity of water in the soil on the one hand, but on the other, trees also withdraw water for their growth. As a result, they compete with intermediate crops. To quantify the net effect of trees on soil moisture, we installed soil moisture sensors in collaboration with Vives. These were placed in a row perpendicular to the row of trees and at four different distances from the trees (1m , 3m, 6m and 9m), each time at two depths: in the soil (20 cm) and under the soil (60 cm). These sensors measure moisture levels daily and remain in place year-round. This allows us to see not only how far the effect of the trees extends, but also how it varies throughout the year. We will only temporarily remove the sensors during fieldwork in function of the crop.

Plaatsen bodemvochtsensoren

2. Light sensors

We placed a transect of 8 light sensors (type pyranometers), 4 of them on each side of the tree row at 3m, 6m, 9m and 12m respectively from the tree row. Every 10 minutes they measure the intensity of incident sunlight. They transmit the data in real time to our server. The sensors are height-adjustable so they are always above the crop. The shadow of our saplings on the intercrops is negligible at the moment, but over the years we will have to take this into account more and more and adapt cultivation technique or (variety) choice. The north-south orientation of our tree rows already ensures that the shadow impact is minimal in the afternoon.

Reeks lichtsensoren op het agroforestryperceel

3. Weather stations

Rows of trees are believed to have a beneficial effect on the microclimate between the rows. For instance, windbreak is thought to reduce evapotranspiration and thus reduce moisture loss in the crop. But trees also influence other factors, such as air and soil temperature or humidity. We placed 3 permanent weather stations on our plot: 1 in the first aisle on the eastern side of the tree row, 1 in the first aisle on the western side and 1 in the middle between two tree rows. The weather stations are equipped with sensors for temperature (soil and air), moisture (soil and air), precipitation, wind (direction and strength) and visible light (PAR). Every 5 minutes, each of those parameters is measured.

Weerstation op het agroforestry perceel

4. Dendrometers

The trees are a productive element on our plot so we will also monitor them. In the meantime one of the trees has been fitted with an electronic dendrometer that measures the thickness growth of the trunk. These meters are so sensitive that they can even detect the difference in trunk thickness between day and night (because of the sap flow). You can see the tree 'breathing', so to speak. We are especially interested in the impact of weather conditions (e.g. periods of drought) over the years on the thickness growth and vitality of our trees. Soon, we will equip another ten trees with an analogue dendrometer on which we can monitor thickness growth every year.

elektronische dendrometer

Nut oil from Rumbeke?

It’s still a distant future, yet we are already thinking about processing the nuts from our trees. There are plenty of ways to market nuts (dry nuts, fresh nuts, nut liqueur, nut paste,...), but we are mainly looking in the direction of nut oil. Depending on the quality of nuts, you get about 1.5 to 2 liters of oil from 10 kg of dry nuts via cold pressing. Assuming a production of 30 kg of dry nuts per tree in a good year and the 47 trees, our plot would yield around 210 to 280 liters of nut oil annually. But before that, the trees will have to grow and receive care for at least another 15 years or so.

Just a few kilometers from our plot in Rumbeke, Christophe and Jens Vancoppenolle recently started 'Nooly', a small-scale and artisanal company that presses nuts, with ambitions to scale up in the future. We were allowed to take a look and get a short demonstration of the processing process. Watch along in the video below.

Notenpersen bij Nooly

What has happened on the plot since the last edition of 'Digging Deeper'?

As you could read above, most of the focus last month was on setting up the sensors. We also applied champost (EC (conductivity) = 5270 µS/cm, pH = 7.6) to each tree bed. A layer about 10 cm thick and 1 meter in diameter. When applying, take care that the mushroom compost doesn’t pile up against the trunk. Mushroom manure or 'champost' consists of horse and chicken manure, straw and lime. It serves mainly as a soil conditioner rather than a fertilizer. Per tree, we applied 2 wheelbarrows (+- 160 liters or 80 kg) of champost. That contains only 125 g of active nitrogen per tree, which is also released slowly.
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