Using carbon dioxide to increase yields

Oct 6, 2009

Like the rest of our researchers, Ventura County UCCE Farm Advisor Oleg Daugovish and Staff Research Associate Maren Mochizuki are busy with many projects. What will be shared with you today is a summary of one of Oleg and Maren’s  projects that have the potential to increase agricultural yields using captured greenhouse gases.

More than 7 billion tons of green house gases (GHG) were released in the United States in 2006. Most of the gases are attributable to the combustion of fossil fuels used for electricity and transportation. While current CO2 capture technology focuses on geological storage, an incentive to capture emissions may be offered by agriculture: CO2 could be supplied to plants for uptake and sequestration as an alternative to underground storage. Agricultural plants with C-3 carbon assimilation pathway have  shown increased productivity at  CO2 levels elevated above the ambient air concentrations. One plant that has such a pathway is the raspberry, which is the fastest growing high value crop in Ventura County (annual value ~$85 million) and appears very suitable for carbon dioxide sequestration: it is a perennial C-3 crop with multi-layered canopy, is grown in tunnels/hoops that protect the CO2 delivery to leaves from wind and rain, and, has existing support structures for the gas delivery system.

Working with collaborators, we evaluated several plant productivity parameters such as fruit yield, berry size, cane size in a large scale replicated study.

The delivery system was successfully designed and installed, applying a total of about 60 tons of CO2 to three specific hoops during the four-month trial. Diurnal measurements of leaf stomatal conductance, CO2 assimilation, and fluorescence showed a mid-day depression, enabling us to make an informed decision about optimum application time.  We avoided application at the time of the day when plants would be unable to take up the applied CO2, thereby minimizing waste.  We found CO2 concentration in the hoops where gas was applied were 20-25% higher than ambient CO2 concentration during delivery periods (8 h/day), generally returning to ambient levels during hours when gas was not applied.  We also found that leaves in the middle and lower canopy, rather than the top, were the most active, prompting us to place our CO2 drip tape for delivery at about 90 cm (35 inches) above ground level.

The number of baskets from the full hoops in which CO2 was applied increased by 36% after CO2 application.  Berry weight also increased 0.1% per berry in the CO2 hoops.  Cane height, number, and diameter as well carbohydrate content of fruit were similar after CO2 application in all measured plants.

Further information about this study can be obtained by contacting our office.