Elevated Atmospheric Carbon Dioxide Effects on Sorghum and Soybean Nutrient Status

Increasing atmospheric carbon dioxide (CO2) concentration could have significant implications on technologies for managing plant nutrition to sustain crop productivity in the future. Soybean ( Glycine max [L.] Merr.) (C3 species) and grain sorghum ( Sorghum bicolor [L.] Moench) (C4 species) were grown in a replicated split-plot design using open-top field chambers under ambient (357 μmol/mol) and elevated (705 μmol/mol) atmospheric CO2. At anthesis, leaf disks were taken from upper mature leaves of soybean and from the third leaf below the head of sorghum for analysis of plant nutrients. Leaf greenness was measured with a Minolta SPAD-502 chlorophyll meter. Concentrations of chlorophylls a and b and specific leaf weight were also measured. Above-ground dry matter and seed yield were determined at maturity. Seed yield of sorghum increased 17.5% and soybean seed yield increased 34.7% with elevated CO2. There were no differences in extractable chlorophyll concentration or chlorophyll meter readings due to CO2 treatment, but meter readings were reduced 6% when sorghum was grown in chambers as compared in l.Contribution of USDA-ARS in cooperation with the Alabama Agricultural Experiment Station.