Night temperature determines nearly half of wheat yield variation globally
Daily minimum temperature (Tmin) is increasing faster than maximum temperature (Tmax). However, the impact of Tmin on crop productivity is barely studied. Effects of environmental covariates on yield were examined using 42 years of trials at 255 sites representing spring wheat regions globally. Grain-filling was the most sensitive growth stage: Average Tmin explained 40% of yield variation, and 52% when also considering radiation, while average Tmax explained just 20% of variation. Yield declined linearly between the observed range from 8 to 22{o}C average Tmin. Generally, a 1{o}C increased Tmin reduced yield by [~]0.5 t/ha, with high radiation partially offsetting negative effects. Average increase of 1.2{o}C at test sites over 42 years reduced yield by more than 10%. Shorter grain-filling duration likely reduced yield, as well as increased nocturnal rate of dark respiration. A better understanding of drivers of variation in respiration and adaptation to warmer nights could generate a step change in wheat yield.