| Plota | Total Nb | Phosphate-extractable organic Nb | Microbial biomass Nc | Hydrolyzable amino acid-Nd |
| (mg N kg−1 dried soil) | ||||
| F | 1514 | 37.8 | 49.4 | 406 |
| F + HC | 2529 | 44.9 | 79.0 | 759 |