What is a greenhouse dehumidifier?
A greenhouse dehumidifier helps in the removal of excess water vapor from within the greenhouse air. It helps in creating a more controllable environment with higher energy efficiency. It also allows the closing of the greenhouse without the risk of an unexpected disease outbreak in the plants.
The fall and spring seasons are when humidity hits the peak and diseases that stem from excess humidity damage the plants.
How does humidity cause diseases in plants?
- On sunny days, the transpiration from plant surfaces and evaporation from soil increases.
- The warm air inside the greenhouse holds this moisture in vapor form
- At night, when the air starts to cool down, condensation occurs and water droplets are formed on the cooler surface, generally the plant leaves.
- This unwanted moisture gives room for the growth of fungal pathogens like powdery mildew.
- Any dripping moisture from condensation on the greenhouse covering also wets the plant surface and causes the spread of pathogens from one plant to another by plant debris and splashing soil.
Benefits of dehumidification:
• Helps in maintaining optimum humidity levels for the plants to grow
• No need to compromise on ideal temperature to gain ideal humidity level
• Reduces chances of plant diseases
• Lesser need for chemical protections like pesticides
• Lesser labor costs and working hours
• Vapor pressure benefits
Tools and methods to reduce humidity levels:
- Bottom heat- Improves air circulation and helps reduce condensation on plant leaves
- Anti- drip plastic- using a wetting agent in the interior surface of the greenhouse to reduce humidity levels
- Ventilation and heating- Allowing the exchange of moist greenhouse air with dry air from outside (ventilation) and to bring the outdoor air to optimum temperatures for plant growth (heating)
How to choose the right dehumidifier for the greenhouse?
There are various types, sizes and strengths od a greenhouse dehumidifier. While choosing the right dehumidifier for a greenhouse factor such as the size of the greenhouse, area that requires dehumidification, air circulation, uniformity and cost must be kept in mind. If a single dehumidifier is placed in the greenhouse with no ducting, then only the area around the dehumidifier will be dry, but areas away from the dehumidifier will definitely not be dried and will have high humidity and vapor levels. Having such a dehumidifier is pointless as the diseases outbreak will end up affecting all the plants regardless of their proximity to the dehumidifier.
What are the desirable humidity levels?
The desire humidity levels generally vary with the desired temperature. These levels are an average accepted rate and specific plants may require certain specific other levels. The most common temperatures are listed below:
• 50 Degrees Fahrenheit- 83% humidity
• 61 Degrees Fahrenheit: 89% humidity
• 68 Degrees Fahrenheit: 91% humidity
• 86 Degrees Fahrenheit: 95% humidity
Humidity management in a greenhouse is a valuable tool that helps in the prevention of fungal diseases in a plant and is a part of the overall Integrated Pest Management. Controlling the humidity inside the greenhouse along with the temperature not only reduces diseases outbreak or the use of chemical pesticides but also ensures that the reentry intervals from pesticide use does not create any issues.