Rising carbon dioxide concentrations and the future of crop production

Impacts of climate changes on crop physiology and food quality

“…Although the mechanisms by which elevated CO 2 decreases tissue concentrations of N (and proteins) are not yet fully understood, such decreases exceed what would be expected if a given amount of N were diluted by additional biomass (Bloom, 2006). It is likely that decreases in tissue N result to some extent from (i) the accumulation of carbohydrates and other organic compounds as a consequence of CO 2 stimulation of photosynthesis (Idso & Idso, 2001), (ii) reduced uptake of N from the soil under high CO 2 due to lower transpiration rates resulting from decreased stomatal conductance (Kimball & Bernacchi, 2006), and (iii) impaired nitrate assimilation associated with decreases in the photorespiration pathway at elevated CO 2 , as found in C 3 species such as wheat and tomato (Bloom, 2006). In contrast, leguminous plants such as soybean, which can largely acquire reduced N through its N-fixing ability, display much smaller changes in leaf N at elevated CO 2 than non-leguminous crops (Ainsworth et al, 2002).…”

“…This has been associated with the fact that elevated CO 2 results in decreased N content (typically by 13-16%) in plant tissues regardless of the CO 2 -enrichment technology (Ainsworth & Long, 2005;Curtis & Wang, 1998). Although the mechanisms by which elevated CO 2 decreases tissue concentrations of N (and proteins) are not yet fully understood, such decreases exceed what would be expected if a given amount of N were diluted by additional biomass (Bloom, 2006). It is likely that decreases in tissue N result to some extent from (i) the accumulation of carbohydrates and other organic compounds as a consequence of CO 2 stimulation of photosynthesis (Idso & Idso, 2001), (ii) reduced uptake of N from the soil under high CO 2 due to lower transpiration rates resulting from decreased stomatal conductance (Kimball & Bernacchi, 2006), and (iii) impaired nitrate assimilation associated with decreases in the photorespiration pathway at elevated CO 2 , as found in C 3 species such as wheat and tomato (Bloom, 2006).…”

“…Higher N fertilization -sometimes several times current levels -can minimize (Bloom, 2006;Stafford, 2008), but not eliminate, the reduced protein concentration associated with increased atmospheric [CO 2 ] (Taub et al, 2008). It should be emphasized that fertilization at such rates would be unfeasible in terms of costs and unacceptable in terms of environmental consequences (Stafford, 2008).…”

Economic impacts of climate-related changes to California agriculture

“…Furthermore, the fertilizing effect of higher carbon dioxide (CO2) concentrations may also inhibit photorespiration in C3 species such as tomato, wheat and barley (Bloom 2006). With temperature changes of up to 2°C, crop yields (especially for cereals) in lower latitudes will fall, whereas higher latitudes are expected to improve (Easterling et al 2007).…”

“…Other crops such as alfalfa, tomato ) and almonds (Lobell and 2009) are less affected and may even face small yield-improvements under higher carbon concentrations. Finally, changes in winter chill (Baldocchi and Wong 2008), nutrient assimilation due to carbon concentrations (Bloom 2006), and number of days within temperature thresholds (Schlenker et al 2007;Schlenker and Roberts 2009) have also been shown to have an effect on crop yields. Effects may also differ due to differences in microclimate between basins (Rosenzweig et al 1996).…”