Elevated carbon dioxide and water stress effects on potato canopy gas exchange, water use, and productivity

Authors: Fleisher, David; Timlin, Dennis; Reddy, Vangimalla

Submitted to: Agricultural and Forest Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2008
Publication Date: 5/23/2008
Citation: Fleisher, D.H., Timlin, D.J., Reddy, V. 2008. Elevated carbon dioxide and water stress effects on potato canopy gas exchange, water use, and productivity. Agricultural and Forest Meteorology. 148:1109-1122.

Interpretive Summary: Atmospheric carbon dioxide concentration is projected to significantly increase over the next several decades. This increase may result in increases in productivity and water use in several crops including potato. Despite its agronomic importance, few studies have evaluated the effects of increased carbon dioxide on potato responses to water stress. A series of experiments were conducted with potato grown in outdoor growth chambers at ambient and elevated carbon dioxide concentrations. Potatoes grown with elevated carbon dioxide had increased yield and decreased water usage during the course of the season in comparison with ambient carbon dioxide plants. This improvement in productivity and water use efficiency was observed at all levels of water stress tested. These results indicate that potato production and water use requirements are likely to improve should projected increases in carbon dioxide concentration prove accurate. These findings can help policy planners evaluate the impact of global climate change on agricultural land use. Scientists can also use the data to develop improved decision support systems for farmers to improve resource management in potato production.

Technical Abstract: The interaction of carbon dioxide (CO2) and drought has not been well studied in potato. Soil-plant-atmosphere research (SPAR) experiments were conducted in chambers maintained at either ambient (370) or elevated (740 ppm) CO2. Varying amounts of irrigation were supplied to each chamber on a daily basis according to 90, 75, 50, 25, and 10 percent of the daily water uptake measured for a control chamber (100 percent) for each CO2 treatment. The response of canopy photosynthesis with light increased for elevated CO2 plants at most levels of water stress. Maximum seasonal values of canopy photosynthesis decreased by more than 50 percent at the lowest irrigation treatment at both CO2 levels as compared to the 100 percent treatment. Water stress also reduced the duration of the growing season. Mid-season specific respiration rates were suppressed under elevated versus ambient CO2, but were not influenced by irrigation treatment. Seasonal cumulative net assimilation declined with increasing water stress but was significantly higher for elevated CO2 treatments at each water stress level. Transpiration and water use was reduced by CO2 enrichment and water stress. End of season water use efficiency for elevated CO2 plants was nearly double that of ambient CO2 plants when expressed on a tuber fresh weight basis. Total biomass, yield, and radiation use efficiency also increased with elevated CO2 at each irrigation level as compared with ambient CO2. The extra assimilate fixed by elevated CO2 plants was partitioned to underground organs, resulting in higher harvest indices at each level of water stress. These results indicate that potato productivity is increased under elevated CO2 as compared with ambient CO2 at a given level of water stress primarily due to increased assimilation rate and partitioning to tubers.