Extended Data Fig. 1: Vegetative biomass responses to crop diversity.

Average vegetative biomass (in g m^-2) of eight monocultures, 24 different 2- and 16 different 4-species mixtures planted with eight different annual crop species in 0.25 m² plots in Switzerland and Spain. Data are mean and 95% CI. n = 762 plots. The statistical analyses (type-I analysis of variance of a linear mixed model and significance tested with the Satterthwaite approximation method) show significant effects of country [F_(1,20.7) = 195.8, P = 5.23×10^-12], country × diversity [F_(1,677.5) = 8.1, P = 0.004], country × species number [F_(1,679.2) = 5.9, P = 0.015], and marginally significant effects of diversity [F_(1,45.1) = 3.7, P = 0.062] on vegetative biomass. See Extended Data Fig. 2 for seed yield and vegetative biomass data of each species in monocultures and 2- and 4-species mixtures in Switzerland and Spain.