56. Evaluating UAV-based vegetation indices and exploration of new wavelengths combination to monitor winter wheat crop nitrogen status

A dynamic fertilization method based on unmanned aerial vehicle (UAV) imagery to estimate crop nitrogen (N) status appears to offer good opportunities to improve N use efficiency. The objectives of this study are to evaluate UAV-based vegetation indices to monitor N status, and to test new wavelengths to improve the measurement and prediction of the nitrogen nutrition index (NNI). Two fields showing various patterns of NNI dynamics were monitored in the North of France. During the first growing season (2019), 14 commonly used vegetation indices (VI) were compared. During the second year (2020), to improve the accuracy in detecting the crop N response, the wheat canopy reflectance at 17 different wavelengths (405 to 945 nm) was measured. At all stages, reflectance at three wavelengths was identified as best correlated to NNI (632, 615, 590 nm), and 780 nm may present a relevant application. Future developments will tend to improve the accuracy of NNI estimation model.