Deriving Maximum Light Use Efficiency From Crop Growth Model and Satellite Data to Improve Crop Biomass Estimation

Maximum light use efficiency (${\text{LUE}}_{\rm{max}}$ ) is an important parameter in biomass estimation models (e.g., the Production Efficiency Models (PEM)) based on remote sensing data; however, it is usually treated as a constant for a specific plant species, leading to large errors in vegetation productivity estimation. This study evaluates the feasibility of deriving spatially variable crop ${\text{LUE}}_{\rm{max}}$ from satellite remote sensing data. ${\text{LUE}}_{\rm{max}}$ at the plot level was retrieved first by assimilating field measured green leaf area index and biomass into a crop model (the Simple Algorithm for Yield estimate model), and was then correlated with a few Landsat-8 vegetation indices (VIs) to develop regression models. ${\text{LUE}}_{\rm{max}}$ was then mapped using the best regression model from a VI. The influence factors on ${\text{LUE}}_{\rm{max}}$ variability were also assessed. Contrary to a fixed ${\text{LUE}}_{\rm{max}}$, our results suggest that ${\text{LUE}}_{\rm{max}}$ is affected by environmental stresses, such as leaf nitrogen deficiency. The strong correlation between the plot-level ${\text{LUE}}_{\rm{max}}$ and VIs, particularly the two-band enhanced vegetation index for winter wheat (Triticum aestivum) and the green chlorophyll index for maize (Zea mays) at the milk stage, provided a potential to derive ${\text{LUE}}_{\rm{max}}$ from remote sensing observations. To evaluate the quality of ${\text{LUE}}_{\rm{max}}$ derived from remote sensing data, biomass of winter wheat and maize was compared with that estimated using a PEM model with a constant ${\text{LUE}}_{\rm{max}}$ and the derived variable ${\text{LUE}}_{\rm{max}}$. Significant improvements in biomass estimation accuracy were achieved (by about 15.0 for the normalized root-mean-square error) using the derived variable ${\text{LUE}}_{\rm{max}}$. This study offers a new way to derive ${\text{LUE}}_{\rm{max}}$ for a specific PEM and to improve the accuracy of biomass estimation using remote sensing.