[en] Fusion cross sections have been determined by detecting evaporation residues from six systems formed by projectiles of ¹⁵N, ¹⁶O and ¹⁹F and target nuclei of ⁵⁴Fe and ⁵⁶Fe at incident energies around the Coulomb barrier. The comparison of the experimental results with the prediction from the one-dimensional barrier-penetration model revealed that the ¹⁶O reactions were not much enhanced, whereas the ¹⁹F fusion reactions at sub-barrier energies are more than ten times higher than the model calculation. The fusion cross sections for ¹⁵N projectiles showed a medium enhancement. The one-dimensional model has reproduced to some extent the experimental data of the ¹⁵N+⁵⁴Fe and ¹⁶O+^54,56Fe systems by making corrections for the quadrupole deformation of the reacting nuclei. However, the ¹⁹F data cannot be described by this model. In order to explain uniformly the cross sections of the six systems we have performed coupled-channel calculations. The ¹⁵N and ¹⁶O data have been reproduced within the experimental error by opening channels for inelastic excitation in the reacting nuclei and those for one-nucleon transfer. For better explanation of the ¹⁹F data, however, an additional channel for the triton transfer was required. (orig.)