Evaluation of the grain yield and nitrogen nutrient status of wheat (Triticum aestivum L.) using thermal imaging

- Lower canopy average temperature was observed for higher wheat biomass and yield.
- Canopy average temperature was stabilized and regulated by plant nitrogen nutrition status.
- Canopy average temperature was negatively correlated with stomatal conductance and transpiration rate.
- A response curve of grain yield and canopy average temperature to nitrogen addition rate was proposed.

Nitrogen (N) supply significantly influences plant growth and crop yields. To investigate the dynamic process of wheat plant responses to nitrogen management, digital infrared thermography was used to detect canopy average temperature (CAT) during different wheat growth stages in three field management experiments, including N applied rates, N application methods and cultivation approaches, which were conducted in 2013-2014 in southeast China. The CAT was reduced with increased N rates, compared to the control (0 N), applications of 300 kg N ha−1 reduced CAT by 14.0%, 10.7% and 9.2% at the tillering, heading and milking stages, respectively. The CAT was also sensitive to N application methods, in which the CAT of the farmers' fertilizer practice (FFP) was lower and higher than that of the optimal N management (OPT) before the heading stage and after the heading stage, respectively. Considering the cultivation approaches, the effects of deep tillage (NC-DP) on the CAT was more efficient than normal cultivation (NC) in wheat production. Lower CAT was observed for higher wheat biomass and yield, as a result of the CAT being somewhat negatively correlated with leaf N content. The wheat yield could be estimated by monitoring the CAT based on the response curves of the grain yield and CAT to the N addition rate, which was associated with stomatal conductance and transpiration rate. In conclusion, our results indicated that canopy temperature may provide an effective tool for dynamical monitoring of wheat growth and yields.