We show that the resonating valence bond (RVB) state of the t-J Hamiltonian can be described within an effective boson-fermion model. We derive a boson-fermion Hamiltonian which describes the lowest order coupling between holons and spinon waves. The RVB order parameter determines a hybridization between the both types of excitations. The effective Hamiltonian is investigated within the lowest order self-consistent conserving diagrammatic approximation. We compare our approach with the phenomenological boson--fermion model (BFM) that is believed to describe the pseudogap phase.