Fig. 6. Discriminant analysis similarity map determined by discriminant factors F1 and F2 for calibration set of the multiple-field soil samples, showing Groups 5 (0.0–0.060 kg kg^–1), 10 (0.061–0.120 kg kg^–1), 15 (0.121–0.180 kg kg^–1), 20 (0.181–0.240 kg kg^–1), and 25 (0.241–0.400 kg kg^–1).