Importance of canopy temperature data for crop heat stress assessments

What is it about?

Even short episodes of heat stress can cause a substantial decline in crop yield. Large scale studies on the impact of heat stress on crop yields generally rely on temperatures measured by standard weather stations at 2m height. We found that air temperature at 2m height is a poor indicator of the temperature in the crop canopy with up to 7°C temperature difference measured in field plots of rye in Northern Germany. The differences in temperatures were mainly controlled by soil moisture content.

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Why is it important?

Neglecting canopy temperatures in crop heat stress assessments results in a strong underestimate of the heat stress impact on crop yield, in particular for temperate climate regions with predominantly rainfed crop cultivation. Irrigation has two positive effects on crop growth and crop yield: reduction of drought stress and reduction of heat stress. The direct impact of the cooling by irrigation needs to be investigated more in detail in future research.