Effects of open-air elevated atmospheric CO2 concentration on yield quality of soybean (Glycine max (L.) Merr)

•Elevated [CO2] decreased the protein and most amino acids concentrations in soybean seeds.•Elevated [CO2] increased fat and two fatty acids (like linoleic acid and palmitic acid) concentrations in soybean seeds.•The total yields of protein and oil will be increased under future elevated [CO2].

Investigations across the world have elucidated common chemical and physiological responses of plants to the influence of elevated atmospheric CO2 concentration ([CO2]). Focus is now turning to the influence of elevated [CO2] on yield quality among a number of globally important crops including soybean (Glycine max (L.) Merr). Soybean cv. Zhonghuang 35 was grown in a free-air CO2 enrichment (FACE) field experiment at Changping-Beijing (China) under ambient (415 ± 16 μmol mol−1) and elevated (550 ± 19 μmol mol−1) CO2 concentrations. Results showed that elevated [CO2] increased the yields of soybean seeds (g m−2) by 26% and 31% respectively, in 2009 and 2011. Total protein concentration in seeds was significantly reduced by 3.3% under CO2 enrichment, but oil concentration increased by 2.8%. Accordingly, most proteinogenic amino acid concentrations were significantly reduced under elevated [CO2], whilst two fatty acids (linoleic acid and palmitic acid) increased in concentration. The protein and oil yield per unit ground area increased by 24.5% and 32.0%, respectively. Results indicate that whilst future elevated atmospheric [CO2] may improve the oil quantity of soybean, corresponding reductions in the nutritive value are likely to occur.