Estimation of chlorophyll content and yield of wheat crops from reflectance spectra obtained by ground-based remote measurements

This study aimed to analyze the relationship between chlorophyll potential, chlorophyll content, and grain yield of different wheat cultivars by using ground remote sensing and laboratory data. Chlorophyll potential is the difference between the reflectance factor integrals with and without chlorophyll absorption (in the 550-730 nm wavelength range). Ground-truth data were obtained at the experimental fields located in the Krasnoyarsk region, Russia (2002-2012). Experiments were conducted in different seasons under various lighting conditions by controlling plants states and soil types. Spectral measurements were obtained using a double-beam spectroradiometer, which was installed on a mobile work platform at a height of 5-18 m. The photometric area varied from 0.5 to 2 m2. The study showed good correlation (R2 = 0.9) between chlorophyll potential and chlorophyll content for different wheat cultivars. However, the correlation between chlorophyll potential and grain yield was less (R2 = 0.8). The values of chlorophyll potentials depended on the type of wheat during the growing season. The novelty of the approach is that it calculates the chlorophyll potential with additional spectral regions when compared with normalized difference vegetation index. We used a spectroradiometer with high spectral resolution. This increased the accuracy and stability of measurements in rapidly changing conditions.