Grain Protein Content in Commercial Wheat Estimated Via Timeseries Plant Traits Retrieved From Sentinel-2 Images by Radiative Transfer Model Inversion

Wheat (Triticum spp.) is widely grown and receives large amounts of nitrogen fertiliser. Grain protein content (GPC) is key to its nutritional and economic value and is influenced by genetic, management and environmental factors. Accurate pre-harvest estimation of GPC patterns could improve N efficiency and profit. Some plant traits with physiological links to GPC have been identified, but assessment of traits retrievable from satellite imagery could advance GPC estimation at commercial scales. By radiative transfer model inversion of Sentinel-2 imagery, we retrieved chlorophyll (C
a+b
), leaf dry matter (C
m
), leaf water content (C
w
) and leaf area index (LAI) for > 6,000 hectares of commercial wheat across two years. Farmers supplied ~90,000 GPC data points collected during harvest. Using a gradient boosted machine, we predicted GPC (R
²
= 0.86, RMSE = 0.56) and found that C
w
explained most GPC variability under stress conditions but that contributions to GPC were distributed among plant traits in milder conditions.