Free air CO 2 enrichment (FACE) improves water use efficiency and moderates drought effect on N 2 fixation of Pisum sativum L.

Background and aims Legume N2 fixation is highly sensitive to drought. Elevated [CO2] (e[CO2]) decreases stomatal conductance (gs) and improves water use efficiency (WUE), which may result in soil water conservation and allow N2 fixation to continue longer under drought. Using a Free-Air CO2 Enrichment (FACE) approach, this study aimed to elucidate whether e[CO2] improves N2 fixation of Pisum sativum L. under drought.