Growing Concern: Greenhouse Condensation

Humid
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If you’re experiencing condensation inside of your greenhouse you might be growing more than just plants. Moisture can be a good thing, and for some plants it is essential in their survival, but if condensation is dripping on your plants it could be creating ideal conditions for mold and plant diseases. Below you will find some techniques suggested by the Food, Agricultural and Biological Engineering (FABE) department at Ohio State University (OSU) that can help you have a drier greenhouse environment.

What is condensation?

Before you address your issue with condensation it helps to understand the factors that cause it. Air and water vapor are constantly surrounding us. As temperatures fluctuate the amount of water vapor that can be stored in the air also varies. An increases in temperature will expand the air allowing it to hold more moisture. A decrease in temperature will contract the air reducing how much moisture it can store. When warm air hits a cold surface the air at the contact point condenses resulting in excess moisture on the surface in the form of water droplets. This process can happen often in a greenhouse because the temperature of the plants and greenhouse cover change under various conditions like the transition from day to night.

Why is condensation dangerous for your plants?

If water is constantly dripping onto your plants it can interfere with the intensity of the light reaching those plants, which can harm their quality. In addition, wet plants are the perfect victim for molds and disease, as they thrive in wet environment. Therefore, a drier greenhouse environment is a powerful defense against some plant diseases.

Downy_and_Powdery_mildew_on_grape_leaf
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“A water film on a plant provides the ideal condition for plant diseases such as Botrytis cinerea (gray mold), downy mildew, and white rust to grow and infect crops.” –OSU

How can you prevent greenhouse condensation?

There are some simple and practical things growers can do to reduce greenhouse moisture problems. The FABE department at OSU published an article explaining some methods for keeping the surface of your plants dry and disease free. They suggest that growers adopt these following climate control techniques to reduce condensation on plants and greenhouse coverings:

Bottom Heating and Between-Row Heating:

Keeping plant surface temperatures above the dew point prevents condensation. Locating the heating distribution system nearer or below the crops can improve the micro-climate by providing heat more directly to the plants and by stimulating air circulation.

Keeping Plants Warm with Thermal Screens:

Providing better insulation using thermal screens is another way to keep the climate warmer. However, thermal screens require special attention to humidity build-up under screens and condensation on the material.

Air Circulation:

Circulating air with horizontal air flow (HAF) fans or a Fanjet and perforated poly tube often alleviates mild humidity problems. The circulation distributes warm air around the plants and encourages evaporation of the condensate into the air.

Heating and Ventilation:

In combination, this is the most common method of dehumidification in a greenhouse. Ventilation brings in air, which is heated, allowing it to absorb some of the moist air from the building before exhausting it to the outside. The increased heating load can be expensive, and heating-ventilation control should be considered carefully.

Purchase the Proper Cover Material:

Condensation is not a problem on the greenhouse cover unless it is falling on your plants. Coverings and screens are often coated with anti-condensation additives or wetting agents that prevent dripping, and gutters are used to trap the water.

In summary, with the proper venting, heating, and circulation tools you can control the moisture in your greenhouse. This environmental control is one of the most important factors in disease prevention, as helps keep your plants dry. Addressing your condensation issues early on is the opportunity to prevent infection and promote a healthy crop.

Do you have any experience with this topic? Has mold ever taken over your crop? How do you prevent it? please leave your thoughts in the comment section below.

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Author: Daniel Monk

Need light-deprivation, rolling benches, a greenhouse or greenhouse accessories? Let me know, and I will get you connected with the right people. Email: ContactDanielMonk@gmail.com Twitter: @DanJMonk Blog: www.DanielJmonk.com - Greenhouse Industry Problems | Solutions | Opportunities

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