Can CO2 enrichment benefit all greenhouse crops?
Written by
Benjamin Miller
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.CO2 enrichment brings about a real increase in photosynthesis with most greenhouse crops, but must be applied carefully. While practically all plants show benefits from higher concentrations of CO2, it must be applied to a greater or lesser extent with certain species than with others. For instance, tomatoes and lettuce show 30-50% increases in yield while orchids respond moderately.
Light Synchronization
- Activate enrichment only above 800 μmol/m²/s light intensity
- Use PAR sensors to measure photosynthetic active radiation
- Align CO2 release with daylight hours for maximum efficiency
- Adjust for seasonal light variations automatically
Concentration Management
- Maintain 800-1200 ppm for most flowering/fruiting crops
- Reduce to 400-600 ppm for leafy greens and herbs
- Monitor continuously with NDIR CO2 sensors
- Prevent overshoot with proportional control valves
Environmental Integration
- Increase temperatures by 2-3°C during enrichment periods
- Maintain humidity at 60-70% for optimal stomatal opening
- Adjust irrigation for increased transpiration rates
- Balance with ventilation to prevent excessive buildup
Proper implementation requires a gradual introduction of CO2. Start enrichment at 400 ppm above ambient levels. Increase the concentration by 100 ppm daily until the desired concentrations are reached. Sudden spikes lead to stomatal closure, reducing photosynthesis efficiency. Watch plants for signs of stress, such as leaf curling.
The light intensity of an environment will directly determine the effectiveness of increased CO2 concentrations. Below 200 μmol/m²/s, the addition of CO2 provides no benefit. Between 400 and 800 μmol/m²/s of light, CO2 enrichment will give a moderate benefit to growth. Above 800 μmol/m²/s, we can expect stronger growth with a saturated photosynthetic response to increased carbon dioxide.
Adjustments to temperature and humidity are beneficial for CO2 enrichment. When enriching, the growing temperature can be increased by 2-3°C above baseline temperatures to enhance metabolic processes further. Regarding humidity, a humidity level of 60-70% is sufficient for growth, keeping stomata open for gas exchange. These manipulations allow for the maximization of carbon fixation efficiency.
Automation systems optimize CO2 delivery with precision. The system continuously monitors light, temperature, and humidity in the growing environment. The controllers will only release CO2 when all the parameters match. This practice minimizes waste while ensuring that crops receive CO2 enrichment during the most ideal growing conditions.
Read the full article: Greenhouse Climate Control: Growth & Efficiency
