ODP: A novel indicator for estimating photosynthetic capacity and yield of maize through UAV hyperspectral images

Abstract

Rapid and accurate monitoring of photosynthetic indicator is of great significance for understanding crop growth and development, and predicting yield. Hyperspectral imagery has become a powerful tool for evaluating photosynthetic capacity due to its non-destructive nature in sensing crop radiation. Most photosynthetic indicators have instantaneous ideal values, which cannot fully reflect the photosynthetic capacity of crop populations in field environments. This study introduces a novel indicator “one day photosynthesis” (ODP) based on the various photosynthetic indicators including net photosynthetic rate (Pn), stomatal conductance (Gs), internal CO₂ concentration (Ci), and transpiration rate (Tr). We performed trend fitting on the time-series photosynthetic indicators obtained at a frequency of two hours, and then calculated the projection area of the fitting curve on the time axis. Later on, the ODP was calculated by assigning weight to the projection area using the CRITIC and correlation method, and the feasibility of ODP was tested using the growth of hundred-grain weight (HGW). Finally, we constructed the ODP estimation model based on canopy hyperspectral data, and further estimated the yield. The results showed that the correlation coefficients between ODP and the growth of HGW were 0.831, 0.882, 0.856, and 0.833 at 10, 20, 30, and 40 days after flowering, respectively. The R² of the ODP estimation model based on hyperspectral vegetation indices (VIs) in the four growth stages were 0.71, 0.83, 0.79, and 0.75, respectively. Moreover, ODP also showed high accuracy and adaptability in different sites, years, sowing dates, and cultivars. We noticed that ODP also has good accuracy in estimating the maize yield, as the R² of estimated yield on the base of measured and estimated ODP was 0.770 and 0.716 respectively. Furthermore, the VIs screened by ODP modeling can also be used for yield estimation, and this VIs screening method is superior to the yield estimation model built based on the correlation between VIs and yield. This study findings provides a novel insight regarding the new ODP indicator that has potential application prospects for efficient estimation of maize photosynthetic capacity and yield.