Canopy spectral reflectance for crop water stress assessment in wheat (Triticum aestivum, L.)*

Spectral reflectance in the near-infrared (NIR) and short-wave-infrared (SWIR) regions shows decreasing water absorption troughs upon crop water stress. In this study, decreasing water absorption troughs were identified from reflectance of irrigated wheat crop. The crop was grown under two different irrigation methods, sprinkler and flood irrigation. Crop reflectance was measured using an ASD FieldSpec 3 (350-2,500 nm) hand-held spectroradiometer at 1 week before the critical growth stages. Among different growth stages, wheat crop was found to be under stress in crown root initiation, jointing, and flowering. Results based on crop yield, and raw and first derivative spectral analysis indicated that flood-irrigated wheat had more stress compared with sprinkler-irrigated wheat. Five water stress-sensitive wavelengths (974; 1,195; 1,455; 1,791; and 1,935 nm) were identified from flood-irrigated wheat. Among them, two wavelengths (974 and 1,195 nm) were found to be highly water sensitive and good indicators for water stress. Detecting crop water stress prior to the critical growth stages of wheat helps in proper irrigation scheduling. (c) 2020 John Wiley & Sons, Ltd.