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Soybean growth and yield response to elevated carbon dioxide

Rogers, H.H., Cure, J.D., Smith, J.M.
Agriculture, ecosystems and environment 1986 v.16 no.2 pp. 113
Glycine max, crop yield, carbon dioxide, water stress, models, environmental factors, harvest index
Soybeans (Glycine max L. Merr. 'Bragg') were grown in seeded rows in open-top field chambers and exposed continuously to a range of elevated CO2 concentrations through-out the 1982 and 1983 growing seasons. During 1983, a water stress treatment was also imposed. Comparison of vegetative growth with a similarly conducted pot experiment showed an increased ration of leaf area to total top dry weight in the seeded row plants, but generally similar qualitative effects of elevated CO2. Careful recording of mainstem leaf emergence rates and reproduction stages showed no consistent effect of CO2 under well watered conditions, but in 1983 there was a distinct modification by high CO2 of the water stress-induced hastening of the time to physiological maturity. In 1982, and for the well watered plants in 1983, standing biomass at maturity was increased significantly by elevated CO2, but harvest index decreased and yield was (statistically) unaffected by the treatment. The yield responses calculated for a doubling of the current CO2 concentrations for these well watered treatments were 1.07 and 0.93, respectively. In the water stress treatment in 1983, however, harvest index did not decrease in the presence of elevated CO2, and a highly significant yield response occurred (1.41 at 700 μll-1).