| Methods | Dose (mg·kg−1) | NVef | MTf | NVef | MTf | |
| Cu(II) mg·kg−1 | Cr(III) mg·kg−1 | |||||
| Mehlich-1 (pH = 1.42) | 0 | 1.53 | 1.53 | 1.53 | 1.53 | |
| 100 | 1.53 | 1.53 | 1.51 | 1.53 | ||
| 400 | 1.53 | 1.53 | 1.51 | 1.53 | ||
| 800 | 1.53 | 1.53 | 1.51 | 1.53 | ||
| Solution KCl 1 mol·L−1 (pH = 5.96) | 0 | 5.08 | 4.97 | 5.08 | 4.95 | |
| 100 | 5.11 | 4.95 | 4.87 | 4.79 | ||
| 400 | 4.96 | 4.85 | 4.77 | 4.68 | ||
| 800 | 4.98 | 4.88 | 4.65 | 4.68 | ||
| Distilled and deionized water (pH = 5.25) | 0 | 6.08 | 6.00 | 6.08 | 6.00 | |
| 100 | 5.97 | 5.83 | 5.75 | 5.72 | ||
| 400 | 5.61 | 5.54 | 5.60 | 5.44 | ||
| 800 | 5.57 | 5.43 | 5.35 | 5.34 | ||
| Solution CaCl2 0.01 mol·L−1 (pH = 5.70) | 0 | 5.30 | 5.20 | 5.30 | 5.20 | |
| 100 | 5.25 | 5.20 | 5.12 | 5.02 | ||
| 400 | 5.17 | 5.05 | 5.04 | 4.95 | ||
| 800 | 5.17 | 5.05 | 4.97 | 4.95 | ||