Research Article
Quick Determination of Soil Quality Using Portable Spectroscopy and Efficient Multivariate Techniques
Table 4
Optimal selection of the preprocessing technique using the IPLS model.
| Parameters | Models | Calibration set (77) | Prediction set (33) | R2 | RMSEC | Bias | R2 | RMSEP | Bias |
| N (%) | RAW | 0.4576 | 0.0361 | 0.0006 | 0.4894 | 0.0390 | −0.0137 | MSC | 0.4710 | 0.0358 | 0.0000 | 0.4891 | 0.0389 | −0.0135 | MC | 0.4991 | 0.0351 | 0.0006 | 0.5138 | 0.0379 | −0.0111 | SNV | 0.4477 | 0.0364 | 0.0000 | 0.4477 | 0.0401 | −0.0131 | FD | 0.4231 | 0.0368 | 0.0012 | 0.4982 | 0.0383 | −0.0119 |
| P (mg·kg−1) | RAW | 0.6194 | 0.9627 | 0.0102 | 0.6445 | 0.9611 | −0.1017 | MSC | 0.5739 | 1.0074 | 0.0037 | 0.5636 | 1.1048 | −0.3496 | MC | 0.5533 | 1.0256 | 0.0322 | 0.5973 | 1.0237 | −0.2469 | SNV | 0.5157 | 1.0582 | 0.0073 | 0.5090 | 1.0876 | −0.2161 | FD | 0.6740 | 0.9087 | 0.0127 | 0.7005 | 0.9029 | 0.1131 |
| K (cmolc·kg−1) | RAW | 0.6170 | 0.1586 | 0.0110 | 0.6229 | 0.1802 | −0.0364 | MSC | 0.7890 | 0.1253 | 0.0020 | 0.7604 | 0.1700 | −0.0864 | MC | 0.6977 | 0.1445 | 0.0010 | 0.6746 | 0.1767 | −0.0569 | SNV | 0.8104 | 0.1184 | 0.0020 | 0.8268 | 0.1476 | −0.0700 | FD | 0.7763 | 0.1275 | 0.0030 | 0.7221 | 0.1642 | −0.0515 |
| Mg2+ (cmolc·kg−1) | RAW | 0.7702 | 0.5029 | 0.0008 | 0.7764 | 0.6087 | −0.0252 | MSC | 0.5490 | 0.6597 | 0.0040 | 0.5817 | 0.7861 | −0.0578 | MC | 0.6285 | 0.6141 | 0.0040 | 0.7510 | 0.6574 | 0.1355 | SNV | 0.5619 | 0.6557 | 0.0108 | 0.5504 | 0.8051 | −0.0274 | FD | 0.5103 | 0.6760 | 0.0040 | 0.5544 | 0.8040 | −0.0526 |
| Ca2+ (cmolc·kg−1) | RAW | 0.6073 | 3.1258 | 0.0313 | 0.5450 | 3.3710 | −0.2670 | MSC | 0.7369 | 2.6520 | 0.0119 | 0.7346 | 2.8916 | −0.9689 | MC | 0.7773 | 2.4693 | 0.0749 | 0.7868 | 2.5842 | −0.7115 | SNV | 0.5755 | 3.2082 | 0.0242 | 0.5809 | 3.2835 | −0.2832 | FD | 0.6646 | 2.9410 | 0.1847 | 0.6218 | 3.2138 | −0.1248 |
| pH | RAW | 0.3762 | 0.7206 | 0.0440 | 0.3209 | 0.6363 | 0.2764 | MSC | 0.5937 | 0.6254 | 0.0048 | 0.6042 | 0.5648 | 0.0948 | MC | 0.5815 | 0.6316 | 0.0021 | 0.4628 | 0.5458 | 0.1008 | SNV | 0.5624 | 0.6425 | 0.0217 | 0.4477 | 0.5901 | 0.0398 | FD | 0.6887 | 0.5648 | 0.0407 | 0.5005 | 0.5301 | 0.1165 |
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