The vapor pressure deficit (VPD) is a measurement of the difference between the amount of moisture currently in the air and the total moisture the air can hold when saturated. It represents the balance between temperature and relative humidity. Maintaining the optimal VPD range is crucial for healthy plant growth and cannabis is no exception.
The vapor pressure deficit directly impacts how efficiently cannabis plants can photosynthesize, transpire, and grow. When VPD is too high, the plant experiences stress. If VPD is too low, issues like mold and rot can occur. Finding the proper equilibrium supports vigorous growth and robust yields. The VPD chart simplifies the process of maintaining the ideal conditions.
The Science Behind VPD
Before delving into the practical applications of VPD charts in cannabis cultivation, it’s essential to understand the science behind them. VPD is typically measured in units of pressure, such as Pascals (Pa) or kilopascals (kPa). In cannabis growth, VPD is a crucial parameter because it directly influences the transpiration process.
Transpiration is losing water through tiny openings in their leaves called stomata. This water loss is necessary for the uptake of nutrients from the roots and the overall growth and health of the plant. When the VPD is too high or too low, it can hinder transpiration, leading to growth problems.
How the VPD Chart Works
The VPD chart displays curved lines representing each growth phase’s optimal temperature and relative humidity combination. For young vegetation in the earliest stages of growth, the target VPD range is 0.6 to 1.0 kPa. For mature vegetative plants, the ideal VPD increases to 0.8 to 1.2 kPa.
Once the flowering stage begins, the goal is to maintain a VPD between 1.0 and 1.5 kPa.
The curved lines on the chart make finding the proper temperature and RH pairing easy. For instance, if the plants are in vegetative growth and the temperature is 80°F, the RH should be around 75% to achieve the ideal 1.2 kPa VPD target. If the temperature drops to 70°F, the humidity should be increased to about 85% to remain in that same VPD range.
Growers use digital sensors to monitor the current conditions in the grow area. They can then adjust humidification, dehumidification, heating, and cooling equipment to reach and maintain the optimal VPD zone displayed on the chart. Sensors should be positioned at the top of the plant canopy to get readings for the microclimate the plants are experiencing.
Benefits of Tracking VPD in Cannabis Growth
Using the VPD chart to balance temperature and humidity offers numerous benefits for cannabis cultivation. Here are some of these benefits:
- Maximizes growth rates – Photosynthesis and other plant processes function optimally within the ideal VPD range, driving faster overall growth. Monitoring VPD allows growers to consistently remain in the optimal zone for vegetative and flowering growth. This means more plant mass and bigger yields.
- Prevents mold and disease – Excess humidity encourages microbial growth. The VPD chart identifies humidity levels that minimize mold risk. Keeping humidity in check based on VPD avoids issues like bud rot and powdery mildew that can destroy crops.
- Avoids plant stress – Temperatures and humidity outside the optimal ranges stress plants and suppress growth. Plants in optimum VPD zones experience less stress and slow development. They have the ideal conditions to reach their full genetic potential.
- Saves energy – Maintaining ideal VPD avoids unnecessary cooling and humidification costs. Closely tracking VPD prevents overcooling, overheating, and wasting money on excessive equipment runtime. Growers spend less to achieve the perfect environment.
- Optimizes yields – Careful VPD monitoring provides what plants need to maximize flower production. Peak harvests depend on keeping plants in the zone for robust growth during every phase. The VPD chart simplifies optimization.
- Improves quality – Proper VPD prevents excess moisture and heat issues that can degrade cannabis quality. Correct humidity and temprature maximize trichome and terpene production for top-shelf cannabis. Controlling VPD maximizes quality just as it does yields.
To Sum Up
As the cannabis industry continues to expand and mature, precision and science-driven techniques are becoming increasingly crucial for growers seeking optimized results. One valuable tool that incorporates scientific principles for cannabis cultivation is the Vapor Pressure Deficit (VPD) chart. VPD charts provide visualized targets for the optimal temperature and humidity pairings at each growth stage, using diagonal curved lines on a grid. By constantly monitoring conditions and adjusting environmental controls to maintain the ideal VPD range, cannabis growers can experience numerous benefits.
Healthier, more vigorous growth results from less plant stress and more efficient photosynthesis and transpiration are achieved within preferred VPD zones. This translates into faster vegetative growth, more extensive flower production, and ultimately higher yields.
Additionally, following VPD chart guidance can help growers save on energy costs by avoiding unnecessary cooling and dehumidification. While VPD charts are an invaluable cannabis cultivation tool, they work best when used holistically with crop steering methods, considering specific strain needs and growth phases. When appropriately incorporated, VPD technology provides an accessible path for growers to enhance plant health, improve consistency, increase yields, and operate more efficiently.
