Improving Jujube Fruit Tree Yield Estimation at the Field Scale by Assimilating a Single Landsat Remotely-Sensed LAI into the WOFOST Model

Few studies were focused on yield estimation of perennial fruit tree crops by integrating remotely-sensed information into crop models. This study presented an attempt to assimilate a single leaf area index (LAI) near to maximum vegetative development stages derived from Landsat satellite data into a calibrated WOFOST model to predict yields for jujube fruit trees at the field scale. Field experiments were conducted in three growth seasons to calibrate input parameters for WOFOST model, with a validated phenology error of -2, -3, and -3 days for emergence, flowering, and maturity, as well as an R-2 of 0.986 and RMSE of 0.624 t ha(-1) for total aboveground biomass (TAGP), R-2 of 0.95 and RMSE of 0.19 m(2) m(-2) for LAI, respectively. Normalized Difference Vegetation Index (NDVI) showed better performance for LAI estimation than a Soil-adjusted Vegetation Index (SAVI), with a better agreement (R-2 = 0.79) and prediction accuracy (RMSE = 0.17 m(2) m(-2)). The assimilation after forcing LAI improved the yield prediction accuracy compared with unassimilated simulation and remotely sensed NDVI regression method, showing a R-2 of 0.62 and RMSE of 0.74 t ha(-1) for 2016, and R-2 of 0.59 and RMSE of 0.87 t ha(-1) for 2017. This research would provide a strategy to employ remotely sensed state variables and a crop growth model to improve field-scale yield estimates for fruit tree crops.