At the very high end of the cultivation spectrum growers are now beginning to rely on calculations of vapor pressure deficit to optimize crops. You may have heard the term before, but what exactly is vapor pressure deficit and why is it so tricky to work with?
What is vapor pressure deficit?
Often, cannabis growers who have their plants in indoor grow rooms with artificial lighting, take into account parameters such as temperature and relative humidity to maximize plant growth and bloom, thus obtaining a harvest of top quality flower. As we will see later, these factors affect different processes of the plant, such as transpiration or nutrient uptake.
However, we usually forget about another important factor that is related to the aforementioned ones: vapor pressure deficit or VPD. In broad terms, VPD is the difference between the amount of water vapor that the atmosphere is able to retain (which depends on temperature) and the amount of water vapor contained in it (relative humidity). It is usually measured in kilopascals (kPa).
Providing plants with a correct relationship between temperature and relative moisture will keep them on the right VPD parameters, increasing the plant’s activity, improving its growth and showing its full potential during the flowering phase. The ideal would be to adjust both parameters (temperature and humidity) to get the best possible VPD value so that the development of plants would be amazing.
However, this approach faces a HUGE obstacle. To optimize the VPD values for plants, often times humidity levels of 65-75% can be needed in warm conditions. This is also very close to the environment you find in a locker room on game day, warm and very humid. And the same thing happens in a grow room that happens in a locker room – you are going to get mold and mildew. At those levels of humidity, there is currently no way around it without using harsh chemical controls that are incompatible with the cannabis industry. So, cultivators have to dial back temp and humidity levels to try and prevent the formation of mold and mildew… and so begins the battle. Your plants like it warm and humid, but so does the mold and mildew, so the battle is always on.
At the University of Cannabis Technology, we are out to advance the art and science of cannabis cultivation and extraction. We believe technology may provide us with a solution to this age-old dilemma, and we are beginning to study it. Commencing this fall (2018), we will be starting a study at 3 major commercial cannabis farms to control mold and powdery mildew under optimal VPD conditions.
This study utilizes a technology that has never been seriously studied on cannabis before, but is generally recognized as safe and effective. While we can’t go into much detail until the study publishes, our scientists are extremely encouraged by initial test results. If successful in solidly controlling mold and mildew under optimal VPD conditions, this study may give us a way to move forward in our goal of reliably growing cannabis under optimal conditions.
Check back with this blog, it will be the first place on the Internet you will find the specifics of this experiment when we are able to disclose them.