| Depth | Test control | Percentage nitrogen in mg N g−1 at Kouoptamo | Percentage nitrogen in mg N g−1 at Foumbot |
| 10 cm | 0.12 ± 0.02 | 0.09 ± 0.04 | 0.16 ± 0.05 |
| 20 cm | 0.15 ± 0.05 | 0.12 ± 0.08 | 0.18 ± 0.07 |
| 30 cm | 0.13 ± 0.03 | 0.15 ± 0.10 | 0.19 ± 0.08 |