Effects of free-air CO2 enrichment (FACE) on the uptake and utilization of N, P and K in Vigna radiata

• Elevated [CO2] decreased N concentration in whole mung bean plants at maturity.
• At maturity, P and K concentration in mung bean was unchanged at elevated [CO2].
• The weight of nodules per plant was significantly increased at elevated [CO2].
• N, P, K-use efficiency in mung bean seed was unaffected at elevated [CO2].

Elevated [CO2] stimulates plant growth, which in turn demands more nutrients to sustain it. The nutrient demand of N-fixing plants may differ from that of other plants under elevated [CO2]. We conducted an experiment to determine how elevated [CO2] affected N, P and K content, assimilation of nutrients and accumulation of metabolites in the legume mung bean [Vigna radiata L.]. We investigated the effect of 550 ± 19 μmol mol−1 [CO2] on N, P, K uptake and utilization by mung bean at the free-air carbon dioxide enrichment (FACE) experimental facility in north China. At maturity, N concentration in whole plants decreased by 4.4%, but P and K concentration was unchanged at elevated [CO2]. The weight of nodules per plant significantly increased at elevated [CO2] but N, P, K-use efficiency for seed and the ratio of seed yield to cumulative absorption of N, P and K was unaffected. These results indicate that under elevated [CO2] the mechanisms governing N absorption and metabolism in mung bean was different from that for P and K. The nutrient dynamics between different elements of overall plant biomass and the soil nutrients pool could, therefore, be changed in future by elevated [CO2].