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Understanding the vapor pressure deficit for optimal cannabis growth

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Understanding the vapor pressure deficit for optimal cannabis growth

Indoor marijuana growers understand that only proper development preparation will result in maximum growth. So, room humidity and temperature balance are essential for quality and great plant productivity.

With basic knowledge of the water cycle and the continuous circulation of water in the atmosphere, you’ll look at its importance in the cannabis industry.

What is then required to create the perfect grow room environment? It involves finding steam pressure deficit Sweet spot.

A common misconception is that cannabis plant transpiration affects the relative humidity in the grow room; However, this is not the case.

It is a good perspective when reading this article that room conditions affect the rate of plant transpiration rather than plant transpiration affecting room conditions. As you will see, plant transpiration leads to plant growth, and causes vapor pressure deficit (VPD) plant transpiration.

Vapor decompression and conditioning systems

Temperature and humidity affect the vapor pressure deficit (VPD). These factors are important to consider when deciding on utility systems, especially when selecting HVAC equipment.

piety is one of the best brands that offer Grow Room HVAC system, which is essential for optimal growing conditions for your plant growth. The HVAC system does this by maintaining the right temperature and humidity in a room, and it comes with the following capabilities:

  • Water extraction: 25 to 272 pints per hour
  • Air flow: 1,500 to 17,000 cubic feet per minute
  • Refrigeration capacity: from 6 to 65 tons
  • Power Supply: 460V/3ph/60Hz, 220V/3ph/60Hz

VPD and transpiration rate

Vapor pressure occurs when a liquid reaches a certain temperature before it turns into vapor. On the other hand, the vapor pressure deficit (VPD) is the difference between the moisture in the room air and the potential room environment that should contain more moisture.

However, the VPD is responsible for a plant process known as transpiration, which directly affects plant health. While transpiration is a process that occurs in plants, water and other essential nutrients pass from one cell to another. It is critical to check the transpiration rate initially because growing VPD cannabis depends on your plants losing moisture through transpiration. The plant’s rate of transpiration is the rate at which it loses moisture as water vapor through its stomata.

Growing cannabis loses 95% to 99% of the water it consumes. This makes it an important step in photosynthesis, which enables plants to take in carbon dioxide. After examining the transpiration process, the next action is to assess your growing environment and whether it will result in healthy, high-quality plants by detecting your VPD. It is calculated by combining temperature and humidity.

A good principle to know is that the amount of moisture in your immediate environment will increase if your VPD becomes too low to support efficient transpiration. This means that the plant is not able to quickly release moisture. Stunted plant growth results from this restriction on the plant’s ability to take extra nutrients and water back to its roots.

The atmosphere is very dry when the vapor pressure difference is very extreme, and transpiration is very rapid. As a result, the plants become stressed and dry. By processing VDP, and thus the metabolic speed of plants, may affect the transpiration rate of plants. Depending on the level of development and maturity of the plant’s root system, the targets of VPD change.

Studying the vapor pressure deficit in depth is crucial to better understanding how it affects your plants. Finding the desired location for the VPD becomes essential at this point. There are two periods that directly affect VPD – SVP and AVP in your grow room.

Saturation vapor pressure (SVP)

There is a maximum allowable temperature for each temperature because the indoor air in your grow room has a maximum vapor capacity before turning back into liquid water. The vapor condenses back into water as dew when this limit is reached. This maximum level of water vapor that the atmosphere can hold is called saturation vapor pressure (SVP).

relative humidity (RH) occurs at this point, at 100%, while VPD is zero. Thus, the SVP represents the maximum amount of moisture the air may contain, varying with temperature; Warmer air can hold extra moisture without saturating it. More vapor can be kept in the air with a larger SVP.

actual vapor pressure (AVP)

This represents the constant water vapor content of the air in your growing environment. This increases and decreases as the rates of transpiration change in your plants. AVP and SVP are linked because the maximum amount of AVP your grow room can handle is the same as SVP. You must fully understand these terms as they will help you in calculating the VPD for your grow room.

Since the AVP can only rise to the current SVP level, any additional evaporated water will become liquid in precipitation. Relative humidity (RH) is a measure of the amount of water vapor in the air relative to its maximum capacity at a given temperature, expressed as a percentage. Now you know that SVP is a vapor that can be held in air at maximum density. The actual amount of vapor in the air is the AVP.

Subtract the maximum value from the actual value to calculate the deficit value.

Simply put, SVP – AVP = VPD


Most growers wonder why a vapor pressure deficit is used instead of RH. VPD is significant because it is directly related to plant transpiration rates, whereas relative humidity does not.

Vapor pressure is responsible for moving water vapor from the leaves and opening the stomata pores for nutrient uptake. You know that increasing room temperature and humidity levels greatly affect VPD. K As a result, maintaining these factors at appropriate levels ensures maximum transpiration for cannabis cultivation.

Grow guide for marijuana beginners.
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