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The 2009 ASHS Annual Conference

Carbon Dioxide Enrichment Increases Yield of Field Grown Red Raspberry Under High Tunnels

Sunday, July 26, 2009
Illinois/Missouri/Meramec (Millennium Hotel St. Louis)
Oleg Daugovish, University of California Cooperative Extension, Ventura, CA
Maren J. Mochizuki, University of California Extension, Ventura, CA
Miguel Ahumada, Driscoll's Berry Associates, Inc., Camarillo, CA
Shawn Ashkan, M.S., Center for Irrigation Technology, California State University, Fresno, Fresno, CA
Carol Lovatt, Univ. of Calif., Riverside, CA
Anthropogenic sources of carbon dioxide (CO2) released into the atmosphere may increasingly affect the global climate system.  While CO2 capture and sequestration is currently costly and underdeveloped, producers of high-value agricultural crops such as raspberry may become advocates for CO2 capture and recycling if substantive benefits to plants can be demonstrated.  We designed a completely randomized study with three replications to optimize a CO2 application system to field grown raspberry (proprietary variety) under high tunnels and to compare plant photosynthesis, growth, and fruit yield with and without CO2.  Leaves at the top of the canopy were 8% less efficient in using available light energy according to leaf fluorescence measurements so we placed the irrigation drip tape to apply CO2 in the middle of the plant canopy.  We found that leaf CO2 assimilation and stomatal conductance were reduced 55% and 30% during the midday, and therefore chose to apply CO2 from 7:00 to 11:00 am and from 2:00 to 6:00 pm.  In this way, we maintained a CO2 concentration of 436 μL·L-1 for four months in tunnels 91.4 m long and 5.5 m wide.  CO2 concentration in the tunnel was 18% higher in the morning hours; wind speed often increased in the afternoon, which may have moved the CO2 even in the protected tunnel.  In CO2 tunnels, yield and berry size from plots 6 m long increased 12% and 5%, respectively, compared to untreated tunnels.  The number of fruit baskets harvested from the entire tunnel increased 36% after CO2 application when compared to previous floricane yield in the same tunnels; the number of fruit baskets also increased 16% in untreated tunnels.  We found no corresponding differential response in leaf CO2 assimilation, stomatal conductance, and fluorescence, raspberry cane height, pruned cane biomass, cane diameter, or carbohydrate content of the fruit after CO2 application; documenting plant physiological changes must be the focus of future research.  As the economic feasibility this system depends on a source of captured or recycled CO2, we hope this study prompts further research and development of CO2 capture and recycling to benefit agricultural producers.