Table 1 List of variables provided via iSDAsoil and average accuracy performance based on the fivefold spatial cross-validation (R-square, RMSE and Concordance Correlation Coefficient). Extractable elements are based on Mehlich-3 method. *Statistics based on the ln-transformed values. See also Supplementary material for detailed summary statistics per variable.
Variable | Unit | Training samples | R-square | RMSE | CCC |
|---|---|---|---|---|---|
Sand content | % | 122,261 | 0.736 | 13.7 | 0.848 |
Silt content | % | 122,223 | 0.640 | 8.92 | 0.780 |
Clay content | % | 122,269 | 0.746 | 9.6 | 0.854 |
Bulk density, <2 mm fraction | g/cc | 13,565 | 0.819 | 126 | 0.901 |
Carbon, organic | g/kg | 122,457 | *0.791 | *0.369 | 0.883 |
Carbon, total | g/kg | 50,140 | *0.794 | *0.291 | 0.820 |
pH in \(\hbox {H}_2\)O | – | 133,378 | 0.818 | 0.459 | 0.900 |
Stone content | % | 92,785 | *0.709 | *0.803 | 0.701 |
Effective Cation Exchange Capacity | cmol(+)/kg | 66,380 | *0.754 | *0.417 | 0.860 |
Calcium, extractable | mg/kg | 144,593 | *0.840 | *0.543 | 0.913 |
Iron, extractable | mg/kg | 57,526 | *0.817 | *0.235 | 0.899 |
Potassium, extractable | mg/kg | 139,122 | *0.773 | *0.509 | 0.872 |
Magnesium, extractable | mg/kg | 136,681 | *0.815 | *0.497 | 0.898 |
Nitrogen, total | g/kg | 99,249 | *0.732 | *0.197 | 0.845 |
Phosphorus, extractable | mg/kg | 53,493 | *0.486 | *0.707 | 0.654 |
Sulphur, extractable | mg/kg | 37,530 | *0.548 | *0.384 | 0.708 |
Zinc, extractable | mg/kg | 39,344 | *0.711 | *0.375 | 0.831 |
Aluminium, extractable | mg/kg | 63,551 | *0.881 | *0.321 | 0.937 |
Depth to Bedrock | cm | 28,054 | 0.429 | 41.3 | 0.725 |
