Empirical model for forecasting sugarcane yield on a local scale in Brazil using Landsat imagery and random forest algorithm

Sugarcane plays an important role in food and energy production in Brazil and worldwide. The large availability of satellite sensors and advanced techniques for processing data have improved the forecasting sugarcane yield on a local and global scale, but more work is needed on exploiting the synergy between remote sensing, meteorological and agronomic data. In this study, we combined such data sources to forecast sugarcane yield using a random forest (RF) algorithm on an extensive area of 50,000 ha, over four years. Images from Landsat satellites were processed to time series of surface reflectance and spectral indices. The approach focused on the development of predictive models which only used data acquired and accessible several months before the harvest. First, three RF models were calibrated with different predictors to forecast the sugarcane yield at harvest: using Landsat satellite images and meteorological data (RF₁); agronomic and meteorological data (RF₂); a combination of Landsat satellite images, agronomic and meteorological data (RF₃). As a comparison, we also tested the influence of including knowledge on the future harvest date in the models RF₂ and RF₃ (RF₄ and RF₅). The average values of R² for RF₁, RF₂, and RF₃ were 0.66, 0.50 and 0.74, respectively. The model with the highest values of R² (RF₃) had a Root Mean Square Error (RMSE) of 9.9 ton ha⁻¹ on yield forecast, approximately 15% of the yield average. Including the harvest date improved the RF₂ and RF₃ models to reach R² = 0.69 and RMSE = 10.8 ton ha⁻¹ for RF₄, and R² = 0.76 and RMSE of 9.4 ton ha⁻¹ for RF₅. A blind forecasting test for the 2016 yields showed similar prediction than the forecast made by in situ field expertise. This result has the potential to assist management of sugarcane production.