Rising global atmospheric CO2 concentration and implications for crop productivity

Authors: Prior, Stephen - Steve; Runion, George; Torbert, Henry - Allen

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/15/2017
Publication Date: 9/15/2017
Citation: Prior, S.A., Runion, G.B., Torbert III, H.A. 2017. Rising global atmospheric CO2 concentration and implications for crop productivity. In: Ribeiro, A., Silva, H., editors. Proceedings of the 5th Simposio Nacional de Agricultura, September 14-15, 2017, Paysandu, Uruguay. p. 197-211.

Interpretive Summary: Carbon dioxide is the first molecular link from atmosphere to biosphere; essential for photosynthesis, it sustains the entire food chain. The level of CO2 in the Earth’s atmosphere is continuing to rise which will affect plant growth. Results from numerous open top chamber field studies clearly showed that growth of most plants (crops and weeds) increased under elevated CO2 with C3 (e.g., soybean) plants showing a much larger aboveground response than C4 plants (e.g., sorgum). Belowground root response was more variable which could be due to sampling methodology. Understanding the whole biological chain of events starting with transfer of C from air to leaf, transformation within the plant, return of plant residue to the soil, decomposition, impacts of other environmental factors (e.g., nutrients and water) and finally C storage within agricultural soils is necessary to optimize agricultural production and to reduce agriculture’s impact on climate change.

Technical Abstract: There is incontestable evidence that the concentration of atmospheric CO2 is increasing. Regardless of the potential impact of this increase on climate change, CO2 will have a direct effect on plants since it is a primary input for growth. Herein, we discuss relative CO2 responses of C3 and C4 plants (crops and weeds) from a series of outdoor studies using open top field chambers; assessments included cash crop yield, crop residue, cover crop, forage, and weed production with associated root information. For some cash crops, relative responses to elevated CO2 for photosynthesis, transpiration, and water use efficiency were evaluated. Results clearly demonstrated that aboveground growth (yield and residue) of most plants increased under elevated CO2, with C3 plants showing a much larger response than C4 plants; belowground root response was more variable. Elevated CO2 increased photosynthesis and decreased transpiration resulting in increased water use efficiency; again, these responses were larger for C3 than C4 plants. Increased growth of invasive weeds suggest that some could become more problematic as CO2 continues to rise. Additional supporting information from these studies show how increased biomass inputs from elevated CO2 affect plant/soil processes including soil structure, residue decomposition, soil C and N dynamics, and enhancement of soil C storage. Understanding the whole biological chain of events starting with transfer of C from air to leaf, transformation within the plant, return of plant residue to the soil, decomposition, impacts of other environmental factors (e.g., nutrients and water) and finally C storage within agricultural soils is necessary to optimize agricultural production and to reduce agriculture’s impact on climate change.