Fig. 5. Maps of the predicted leaf weight (W leaf), leaf N content in the canopy (N leaf) and leaf area index (LAI) at the stage of stem-elongating (15-Aug, 2020) (a-c) and grain-filling (10-Oct, 2020) (d-f) at the experimental site by regressed Gaussian Process Regression (GPR) models. The predicted value (mean) and its standard deviation (STD) were predicted from the GPR models and mapped in each panel. N0, N40, N80, N160, N240 and N320 denote varied nitrogen (N) application rates (see Table 2 for details).