CCH2O Crop Management Bulletin:
By: Erik Biksa
One of the most common mistakes made by experienced sealed room indoor farmers that cost yields is a lack of accurate and replicable humidity management during cropping, ie VPD Humidity Control. The amount of water vapor in the air surrounding the plant’s leaves plays a strong role in regulating the plant’s potential rate of photosynthetic activity–this is what VPD (vapor pressure deficit) is all about. When out of the sweet spot, crops suffer, and can easily be overworked to the point of stress or damage if humidity levels fall too low. Conversely, an overabundance of humidity will stifle growth rates, causing stretchy and weak growth that is prone to problems.
Traditionally, the indoor growers’ focus has been on delivering strong light, adequate mineral nutrition, good air movement, etc. VPD humidity control may be a secondary concern at best, sometimes with growers not realizing that their lack of attention to targeted humidity levels may be the source of problems that are preventing them from reaching their target or forecasted yields.
The majority of the time in a modern sealed grow room, the point of contention that occurs is when there is too great a deficit of water vapor surrounding the leaf in an intensive growing environment designed to push growth rates. When this occurs, the plant is being overworked by light intensity, warm temperatures and excessively dry air–plants struggle to take up and transfer enough water to stay adequately hydrated and avoid cellular damage.
In a modern professionally built and installed sealed grow room, lighting, ventilation, and crop nutrition have typically been very well addressed with today’s sophisticated and specialized cultivation equipment.
On the subject of humidity in sealed grow rooms, Dehumidification is easily accomplished, whether by large dehumidification units or as moisture is removed from the air as condensate by Air Conditioning (HVAC) equipment.
This leaves humidification.
Adding Humidity to the Grow Environment
Yes, adding humidity is very important–counterintuitive when considering historically speaking removing humidity was the focus in traditional mechanically vented grow rooms. However, this has changed–one of the key points of difference in operating a sealed grow room versus mechanically vented grow rooms; the equipment necessary to run a sealed grow room tends to keep the air very dry versus traditional grow rooms.
Here’s a real-world example, and it may sound familiar to growers:
Plants look healthy with lush leaves and aggressive root systems after receiving several weeks of care (whether started as cuttings or seedlings) when coming out of the plant nursery area.
Next, these healthy plants are then transplanted into larger vegetative or flowering areas that provide more space and intensive conditions, ie stronger lighting, air movement, carbon dioxide enrichment, etc.
This is where cropping problems may start– slowed or stalled growth, transplant shock, etc. When VPD (vapor pressure deficit) is managed, healthy plants coming out of the nursery shouldn’t need days to “recover” after transplant–rather, they should come out charging, eager to fill out more allotted space under more intensive conditions after transplant.
If crops appear to stress, curl leaves, slow growth or show other symptoms not present in the nursery growth phase it’s likely an indicator that the correlation between light intensity, temperature and humidity is out of whack.
Importance of VPD Humidity Control
The majority of the time in a modern sealed grow room, the point of contention that occurs is when there is too great a deficit of water vapor surrounding the leaf in an intensive growing environment designed to push growth rates. When this occurs, the plant is being overworked by light intensity, warm temperatures and excessively dry air–plants struggle to take up and transfer enough water to stay adequately hydrated and avoid cellular damage. If pushed past its limits, plants attempt to shut down, ie no more photosynthesis in an attempt to protect and stay alive; the plant’s natural reaction to extreme conditions.
Accurate VPD humidity control and monitoring with effective humidification can fill the gap until the plants develop enough canopy relative to the growing environment to create the right balance of water vapor in the air (plants can humidify their own environment in a sealed room, given the opportunity to gain enough healthy stature).
Equipment for Humidity Control
If you have ever tried to humidify a grow room, ie add water vapor, when plants are smaller and light intensity is bright with air conditioners cycling, you’ll know it can be near impossible to keep up with traditional humidifiers (that are designed for spaces with low to minimal air exchange). Besides often being ineffective in meeting the demand to humidify dry grow room air, traditional humidifiers can become a source of pathogens for crops, as biofilms, bacteria and fungi may develop in humidification pads, reservoirs, or in stagnant water that occurs when the system isn’t cycling, for example during grow room dark hours.
Steam-based humidification systems are energy-intensive and add heat load, requiring additional cooling power.
For the serious-minded grower, typically operating multiple grow rooms within a dedicated operation, the Aguatronics Commercial Humidification System (CHS) is available from Current Culture H2O, your trusted name as a cultivation solutions provider.
CCH2O looked high and low for a crop humidification system that met our growing standards, delivering scalable, reliable, and repeatable results for all of our valued clients’ cultivation facilities.
Part of our criteria was a system that is capable of delivering an ultra-fine fog (less than ten-micron droplet size) in high volumes with a wide and even rate of dispersal from a single fog head. We also demanded that the system be easily scalable, both from an installation and economics standpoint. We also knew the system would have to be compact and not take up space or interfere with existing grow room layouts.
The Aguatronics Facility Commercial Humidification System has met and even exceeded our criteria, allowing for up to six fog nozzles to operate from a single room control–providing coverage for individual rooms up to 30,000 Cubic Feet in volume.
The system operates by drawing fresh RO filtered water and using a screw-type compressor to pressurize the system (using supplied booster pump, filters, and controls) to 30-40 PSI while delivering flow rates of 1 US GPH per compact and directable fog nozzle.
Because only fresh RO water is used on-demand, there is little risk of contamination and there are no bio or mineral residues or deposits that will occur on crops or equipment from dry fog dispersion. The ultra-fine RO water droplets are well distributed by the fog nozzles, which become part of the grow room air movement patterns for even humidity levels throughout the entire cropping area. The system is especially effective when used in conjunction with HAF or Vosterman V-FLO vertical air distribution fans.
Taking control of VPD in the growing area with a professional level grow room humidification system will ensure plants are never stressed from water vapor pressure deficit and ensure a flawless transition with no downtime in growth and development after transplant from the crop nursery.
Choosing the right humidification system will allow you to achieve your target VPD humidity control levels based on your particular growing environmental trends (VPD) and prevent unwanted problems from systems that simply weren’t designed for growing crops under modern indoor agricultural conditions.
To learn more about Aguatronics Commercial Humidification Systems, you can see more here https://cch2o.com/aguatronics-facility-commercial-humidification-system/ or email us HERE for a facility-specific quotation.
Above: Typical Aguatronics Facility Commercial Humidification Systems installation, multiple rooms, central humidification equipment area.
Did You Know: Plants suffering prolonged periods of Vapor Pressure Deficit are significantly more at risk to both root and aerial pathogens & pests. Plants don’t have bones–they use water pressure to maintain their physical structure, when weakened, they are prone to a wide array of common crop problems that can hurt your bottom line.
Optimal Humidity Levels, Cannabis Production–Sealed Environments:
Clone: 75 to 85%
Early Veg: 65 to 75%
Veg: 65 to 70%
Early Flower: 60 to 65%
Mid Flower: 55 to 60%
Late Flower/Ripening: 45 to 50%
*See our General Recommendations for optimal cultivation environment conditions.