Substrate / soil moisture sensor installation instructions and troubleshooting
In order to get representative substrate moisture (volumetric water content, VWC) measurements using the Folium Substrate Moisture sensor, it is important that the sensor is installed correctly.
Installation instructions
- Fully insert the sensor into the substrate/soil (including the black plastic base) ensuring no air gaps left between sensor and substrate/soil as shown in Figures 1 and 2 below.
- Pack substrate/soil around the sensor to fully cover the black plastic base and a few cm of the wire. Sensor installation should allow the distances to the wall, bottom of the pot and top soil surface as shown in figure 1.
Figure 1: Folium Substrate Moisture sensor placement in substrate/soil (source)
Figure 2: Folium Substrate Moisture sensor in coco-coir 50/50 substrate/soil
Placement
The volume of influence of the Folium Substrate Moisture sensor is 240 mL. The sensor readings are representative of an integrated volume of 240 ml substrate/soil around the sensor when installed as shown in figure 1.
Through preliminary field tests, we have found that a 5 - 10 cm distance of the Folium Substrate Moisture sensor from the dripper provides a representative moisture reading of the pot (Figure 3).
However, understanding of the wet bulb formation in the substrate/soil based on the irrigation/fertigation set up and schedule would further help determine the placement of the Folium Substrate Moisture sensors.
Figure 3: Folium Substrate Moisture sensor placement in substrate/soil (preliminary field tests)
Sensor readings are affected by:
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Uniformity of the substrate/soil: uniformity of the substrate/soil components, air gaps, pot to pot differences
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Sensor placement (depth, distance from the wall/bottom of the pot, plant)
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Plant roots: as the plant grows and roots develop, the sensor readings can be affected
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Distribution of water/nutrient mix in the substrate/soil
Therefore, we recommend identifying the ideal location of the pot that meets the installation placement requirements.
Once identified, install the sensor and take the substrate moisture (VWC) readings. Repeat this for a couple more locations and in different pots to make sure the readings are representative of the pots. Then install the sensor in selected location and start collecting data.
As the roots grow the substrate/soil structure may change and and it may affect the readings as well.
Placing multiple sensors in the same pot/bag/soil
If more than one sensor is required to place in one pot/bag for measurement/testing etc. please make sure the volume of influence for each sensor in the bag doesn’t overlap (Figure 4) and the sensor is placed according to the requirements shown in Figure 1 for Folium Substrate Moisture sensor. The volume of influence for Folium Substrate Moisture sensor is different from other sensors substrate/soil sensors.
Figure 4: Non-overlapping volumes of influence for placing more than one sensor in the same pot