Property Model Calibration (n=260) Calibration (n=260) Calibration (n=260) Calibration (n=260) Calibration (n=260) Validation (n=112) Validation (n=112) Validation (n=112) Validation (n=112) Ranking Ranking Ranking
Optimization parameter(s) R2c MBE c RMSE c RPD c R2p MBEp RMSEp RPDp Performance Calibration Validation Overall
pH MARS - 0.90 -0.003 0.34 2.98 0.56 -0.09 0.68 1.21 C 1.00 4.25 2.63
log10 PCR PC = 16 0.75 -0.011 0.50 2.01 0.60 0.04 0.54 1.51 B 3.50 2.25 2.88
PLSR PC = 11 0.75 0.003 0.50 2.03 0.62 0.05 0.56 1.47 B 2.75 2.75 2.75
RF mtry = 94 0.63 -0.070 0.63 1.60 0.56 -0.08 0.59 1.39 C 4.75 3.25 4.00
SVR γ =0.125 , c = 2 0.89 -0.008 0.35 2.89 0.66 0.04 0.51 1.62 B 2.00 1.00 1.50
EC MARS - 0.95 -0.05 1.45 3.68 0.66 0.86 3.88 1.40 B 1.25 4.50 2.88
BoxCox PCR PC = 17 0.78 -0.14 2.79 1.91 0.70 0.38 3.13 1.74 B 3.75 3.00 3.38
PLSR PC = 13 0.78 -0.05 2.74 1.94 0.70 0.37 3.13 1.74 B 3.50 2.00 2.75
RF mtry = 210 0.78 -0.26 2.99 1.78 0.65 -0.12 3.30 1.65 C 4.75 3.50 4.13
SVR γ =0.0019, c = 128 0.92 -0.03 1.92 2.76 0.80 0.30 2.64 2.06 A 1.75 1.00 1.38
SOC MARS - 0.88 1.43 1.50 0.41 0.47 1.51 1.70 0.37 C 3.50 4.50 4.00
BoxCox PCR PC = 36 0.65 1.38 1.46 0.42 0.58 1.51 1.67 0.38 C 2.75 3.75 3.25
PLSR PC = 36 0.73 1.39 1.46 0.42 0.62 1.42 1.53 0.41 C 2.75 2.00 2.38
RF mtry = 140 0.34 1.38 1.51 0.41 0.38 1.37 1.48 0.43 C 4.25 2.00 3.13
SVR γ =0.0078 , c =32 0.83 1.39 1.44 0.43 0.52 1.40 1.54 0.41 C 1.75 2.75 2.25
BD MARS - 0.89 0.00 0.10 2.60 0.28 0.04 0.33 0.75 C 2.00 3.75 2.88
log10 PCR PC = 23 0.55 0.00 0.20 1.36 0.49 0.03 0.23 1.08 C 3.25 2.75 3.00
PLSR PC = 18 0.60 0.00 0.19 1.46 0.52 0.03 0.22 1.13 C 2.75 1.25 2.00
RF mtry = 140 0.36 0.00 0.24 1.14 0.39 0.05 0.22 1.12 C 4.00 3.00 3.50
SVR γ =0.125 , c = 2 0.99 -0.01 0.05 5.94 0.38 0.03 0.23 1.08 C 1.50 3.25 2.38
N MARS - 0.87 0.10 35.16 2.49 0.47 4.08 87.29 0.95 C 1.00 3.75 2.38
log10 PCR PC = 27 0.67 -2.55 53.73 1.63 0.58 -8.80 62.08 1.34 C 3.50 1.25 2.38
PLSR PC = 16 0.68 -2.59 52.86 1.66 0.50 -4.90 62.68 1.33 C 3.00 2.00 2.50
RF mtry = 210 0.33 -1.33 75.86 1.16 0.31 -10.94 75.96 1.09 C 4.00 4.00 4.00
SVR γ =0.0019 , c = 256 0.75 -5.95 50.52 1.74 0.51 -14.88 69.38 1.20 C 2.50 3.00 2.75
P MARS - 0.80 -1.12 10.75 1.80 0.05 3.18 40.63 0.42 C 1.00 4.00 2.50
log10 PCR PC = 39 0.49 -3.14 16.55 1.17 0.26 -3.06 18.45 0.92 C 3.75 2.25 3.00
PLSR PC = 27 0.54 -2.52 15.95 1.21 0.33 -3.41 19.09 0.89 C 2.00 2.50 2.25
RF mtry = 94 0.28 -3.52 19.50 0.99 0.28 -4.55 19.68 0.86 C 5.00 3.75 4.38
SVR γ =0.0019, c = 4 0.46 -3.09 16.14 1.20 0.29 -3.20 14.86 1.14 C 3.25 1.50 2.38
K MARS - 0.88 -43.62 346.90 2.38 0.29 260.77 1199.59 0.66 C 2.00 4.75 3.38
BoxCox PCR PC = 24 0.45 -104.36 692.04 1.19 0.44 41.08 615.80 1.29 C 3.75 2.25 3.00
PLSR PC = 16 0.48 -106.58 685.32 1.20 0.46 35.46 604.31 1.31 C 3.25 1.25 2.25
RF mtry = 140 0.39 -166.50 744.53 1.11 0.36 23.06 700.73 1.13 C 5.00 2.50 3.75
SVR γ =0.125, c = 1 0.95 -27.59 246.34 3.35 0.24 60.93 772.56 1.03 C 1.00 4.25 2.63
Na MARS - 0.87 -0.98 10.65 1.79 0.30 2.25 29.00 0.58 C 1.25 4.00 2.63
BoxCox PCR PC = 14 0.34 -3.29 20.34 0.94 0.15 1.80 17.83 0.95 C 4.25 2.00 3.13
PLSR PC = 8 0.29 -1.96 18.94 1.01 0.13 1.48 18.00 0.94 C 3.50 2.50 3.00
RF mtry = 140 0.38 -2.20 20.54 0.93 0.06 0.15 21.08 0.80 C 4.25 3.50 3.88
SVR γ =0.0019, c = 64 0.74 -0.66 15.67 1.21 0.55 4.81 20.63 0.82 C 1.75 3.00 2.38
Ca MARS - 0.81 -0.09 1.60 1.78 0.29 0.31 3.10 0.88 C 1.75 4.00 2.88
BoxCox PCR PC = 37 0.56 -0.28 2.15 1.32 0.41 -0.08 2.31 1.18 C 3.50 1.75 2.63
PLSR PC = 23 0.51 -0.17 2.28 1.25 0.43 -0.11 2.27 1.20 C 4.00 1.25 2.63
RF mtry = 210 0.34 -0.14 2.35 1.21 0.27 0.05 2.55 1.07 C 4.50 3.00 3.75
SVR γ =0.0078, c = 16 0.77 -0.06 1.49 1.91 0.40 0.53 2.60 1.05 C 1.25 3.50 2.38
Mg MARS - 0.89 -0.09 1.37 2.36 0.58 0.33 2.99 1.22 C 1.25 4.25 2.75
BoxCox PCR PC = 33 0.67 0.03 2.02 1.60 0.61 -0.17 2.27 1.60 B 2.50 1.00 1.75
PLSR PC = 22 0.67 -0.09 2.09 1.55 0.60 -0.31 2.35 1.54 B 3.50 2.00 2.75
RF mtry = 63 0.42 -0.20 2.65 1.22 0.59 -0.70 2.56 1.42 B 4.75 3.75 4.25
SVR γ =0.0039, c = 64 0.85 -0.08 1.51 2.15 0.59 0.09 2.53 1.43 B 1.75 2.50 2.13
S MARS - 0.93 -0.08 6.58 2.82 0.58 2.62 15.43 0.93 C 1.75 4.25 3.00
BoxCox PCR PC = 48 0.81 -1.21 10.38 1.79 0.75 0.89 11.57 1.24 C 3.75 2.00 2.88
PLSR PC = 25 0.80 -0.62 10.04 1.85 0.76 0.39 11.33 1.27 C 3.25 1.00 2.13
RF mtry = 94 0.50 -1.89 15.26 1.22 0.58 -0.73 12.38 1.16 C 5.00 2.75 3.88
SVR γ =0.0039, c = 128 0.96 -0.41 5.79 3.21 0.54 0.91 14.45 0.99 C 1.25 4.00 2.63
Fe MARS - 0.94 1.88 22.57 3.35 0.49 -5.96 86.49 0.52 C 1.25 4.50 2.88
BoxCox PCR PC = 28 0.77 -2.48 46.91 1.61 0.71 -2.56 47.09 0.95 C 4.00 3.00 3.50
PLSR PC = 36 0.80 -1.02 48.00 1.58 0.82 6.16 39.62 1.13 C 4.00 1.25 2.63
RF mtry = 94 0.92 -0.65 29.60 2.56 0.72 -0.14 40.17 1.11 C 2.50 2.00 2.25
SVR γ =0.015, c = 32 0.92 0.18 26.39 2.87 0.74 3.41 48.91 0.91 C 1.75 2.75 2.25
Mn MARS - 0.93 -0.25 3.19 2.25 0.32 4.05 13.73 0.56 C 1.75 3.75 2.75
BoxCox PCR PC = 42 0.66 -1.10 6.44 1.12 0.73 -0.84 6.20 1.24 C 3.50 1.75 2.63
PLSR PC = 24 0.74 -1.25 6.56 1.10 0.52 -0.89 6.04 1.28 C 4.00 1.75 2.88
RF mtry = 63 0.17 -0.99 8.69 0.83 0.23 -0.23 7.05 1.09 C 4.50 2.75 3.63
SVR γ =0.125 , c = 2 0.99 -0.72 2.16 3.34 0.19 0.08 7.46 1.03 C 1.25 3.50 2.38
Cu MARS - 0.92 -0.08 1.39 3.02 0.22 0.16 5.18 0.70 C 1.00 4.00 2.50
BoxCox PCR PC = 34 0.65 -0.09 2.69 1.57 0.39 -0.20 3.17 1.15 C 2.75 2.75 2.75
PLSR PC = 18 0.59 -0.13 2.92 1.44 0.40 -0.27 3.12 1.17 C 4.00 2.00 3.00
RF mtry = 140 0.46 -0.18 3.35 1.26 0.39 -0.09 3.12 1.17 C 5.00 1.75 3.38
SVR γ =0.0019, c =256 0.77 -0.11 2.21 1.90 0.39 0.23 3.33 1.09 C 2.25 3.00 2.63
Zn MARS - 0.79 0.01 0.72 1.83 0.24 0.22 1.48 0.73 C 1.50 4.50 3.00
BoxCox PCR PC = 24 0.60 -0.05 0.94 1.40 0.58 -0.04 0.86 1.26 C 3.75 2.25 3.00
PLSR PC = 21 0.66 -0.03 0.88 1.49 0.51 0.01 0.84 1.30 C 2.75 2.00 2.38
RF mtry = 210 0.43 0.02 1.08 1.21 0.49 0.08 0.88 1.24 C 4.25 3.50 3.88
SVR γ =0.0019, c = 256 0.78 -0.01 0.69 1.91 0.63 -0.07 0.73 1.48 B 1.25 1.25 1.25
B MARS - 0.88 0.06 4.03 2.42 0.57 0.22 8.73 1.22 C 1.00 4.00 2.50
BoxCox PCR PC = 38 0.79 -0.63 5.16 1.89 0.73 -1.79 6.12 1.74 B 3.00 1.50 2.25
PLSR PC = 19 0.77 -0.62 5.37 1.81 0.72 -1.93 6.31 1.69 B 3.50 2.50 3.00
RF mtry = 210 0.59 -1.00 6.68 1.46 0.66 -1.47 6.89 1.55 B 4.75 3.50 4.13
SVR γ = 0.001953, c = 128 0.81 -0.11 4.95 1.97 0.67 -1.09 6.61 1.61 B 1.75 2.50 2.13