VPD is a method to detect crop stress, especially useful in greenhouse. VPD depends on air temperature and relative humidity. VPD provides better estimation than humidity alone because it calculates the ability of air to hold more vapor then it is currently having. VPD is measured in KPa
VPD influences following important growing factors
- Opening of stomata
- Uptake of CO2
- Transpiration
- Nutrient intake by roots
- Plant stress
What happens if VPD is too low.
Plant is unable to evaporate water and transport minerals to plant cells
If VPD is extremely low, water will condense on the leaves, trunk and fruits and create favorable conditions for pests and diseases
When plant is unable to evaporate water, excessive pressure in the plant’s cells can cause cracking of fruits.
What happens when VPD is too high
Evaporation of water from the leaves can exceed uptake of water from the roots. Stomata will close and photosynthesis decrease or stop. After stomata closes, leaves can be injured by heat because they are unable to cool down by evaporating water.
Plants may curl their leaves to save moisture. This will significantly worsen the crop growing rate and quality.
What is optimal VPD
Optimal VPD depends on the plant type and its growing stage
For most of plants, optimal VPD is between 0.8 and 1.2 KPa. VPD below 0.4 and above 1.6 is critical and should be avoided.
How to monitor VPD
Install AgrioSens in greenhouse with air temperature, humidity sensor. Optionally, leaf temperature sensors can be connected for more accurate results. AgrioSens sends data to AgriCommander cloud platform every 10 minutes. AgrioCommander calculates VPD and shows to the user. It is possible to send a warning when VPD is out of optimal range.
This is an example of monitoring of VPD in greenhouse growing tomatoes by AgrioSens. As it can be clearly seen, VPD in this greenhouse is too low. Plants are unable to absorb nutrition from the soil and are susceptible to fungal growth and diseases.
Are plants under stress in your greenhouse?
As we could see in this example, monitoring in greenhouse is very Important. It allows improving your crop quality, saving water, pesticides and fertilizers, avoiding diseases. If you would like to know more about our technology, please contact our sales team.