Research note

Effect of CO₂ levels on greenhouse yield

CO₂ enrichment is one of the higher-leverage levers in greenhouse production, with the effect depending heavily on crop type, baseline CO₂, and climate.

• ~550–650 ppm → +18% yield (C3 crops)

  A moderate elevation to ~550–650 ppm raises yield of C3 crops (tomatoes, cucumbers, lettuce, most greenhouse vegetables) by an average of 18%. C3 plants respond strongly because they lack efficient mechanisms to cope with CO₂ scarcity.

  Source: PubMed Central
• 700–900 ppm → ~+30% average yield

  Older work pushing into the optimal 700–900 ppm band found elevated CO₂ increased the average yield of all plants tested by approximately 30%, with the optimal concentration for growth in the range of 700 to 900 ppm.

  Source: NIH
• Vegetable number +32%, mass +11%

  A meta-analysis of vegetables found an increase in vegetable number (yield) by on average 32% and vegetable mass by 11%.

  Source: NIH
• Correcting depletion matters most

  The biggest gains come from correcting depletion, not just enriching above ambient. In a relatively airtight greenhouse, uptake of CO₂ by the crop can drop daytime CO₂ levels to only 100–250 ppm — below the ambient level of 350–450 ppm. So a meaningful chunk of the benefit is simply preventing the canopy from starving the plants during peak photosynthesis. Crop yield is more heavily dependent on CO₂ at lower concentrations (below 450 ppm) than at higher ones — diminishing returns set in as you climb.

  Source: NIH · PubMed Central

So a practical target band is roughly 700–900 ppm during daylight, with continuous enrichment beating intermittent — and with the understanding that the control logic should back off during heavy ventilation periods, where the CO₂ would just be wasted.

Disclaimer: The precise yield uplift varies by crop and setup — on-site trials beat published averages.

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