Are we approaching a water ceiling to maize yields in the United States?

While annual precipitation in much of the US Corn Belt is likely to remain constant, atmospheric vapor pressure deficit ( VPD ), the driver of crop water loss (evapotranspiration; ET ), is projected to increase from ~2.2 kPa today to ~2.7 kPa by mid‐century primarily due to the temperature increase. Without irrigation, it has been hypothesized that the increase in VPD will create a ceiling to future increases in maize yields. We calculated...