Elevated CO2 reduces nitrate inhibition of N2 fixation in Pisum

Additional carbohydrate supply resulting from enhanced photosynthesis under predicted future elevated CO₂ is likely to increase symbiotic nitrogen fixation in legumes.

Butterly et al. use free-air CO₂ enrichment (FACE) to study field pea, Pisum sativum, growing under different levels of CO₂ and N supply in a semi-arid cropping system and find that increasing N reduces nodulation at ambient CO₂ but this inhibitory effect is less under elevated CO₂. The results indicate that field pea may perform well in semi-arid agricultural systems under future CO₂ concentrations irrespective of soil N status and subsequent gains in N input via enhanced N₂ fixation will be important for maintaining the N fertility of cropping systems.