Elevated CO₂ increases biomass and tuber yield in potato even at high ozone concentrations

•  Changes in the growth and yield of field-grown potato (Solanum tuberosum cv. Bintje) induced by season-long elevated CO₂ and/or ozone concentrations are reported. •  Open-top chambers and unchambered field plots were used to examine crop responses to three CO₂ (ambient, 550 and 680 µmol mol^-1 ) and two ozone (ambient and 65 nmol mol^-1 , 8 h d^-1 seasonal mean) treatments applied throughout the 105 d growing season. •  Elevated CO₂ increased both above- and below-ground biomass at intermediate and final harvests. Tuber yield at final harvest was increased by c. 40% due to an increase in mean tuber weight rather than tuber number; tuber yield did not differ significantly between the 550 and 680 µmol mol^-1 CO₂ treatments. Elevated ozone had no significant effect on growth or yield except for the largest size category of tubers, despite extensive visible foliar injury. Significant CO₂  × ozone interactions were detected only for senescent leaf number and green leaf ratio. •  Elevated CO₂ increases biomass and tuber yield in S. tuberosum cv. Bintje even at high ozone concentrations; these findings are discussed in relation to predicted future atmospheric changes.