  It is well established that at low energies one-dimensional (1D) fermionic
systems are described by the Luttinger liquid (LL) theory, that predicts
phenomena like spin-charge separation, and charge fractionalization into chiral
modes. Here we show through the time evolution of an electron injected into a
1D t-J model, obtained with time-dependent density matrix renormalization
group, that a further fractionalization of both charge and spin takes place
beyond the hydrodynamic limit. Its dynamics can be understood at the
supersymmetric point (J=2t) in terms of the excitations of the Bethe-Ansatz
solution. Furthermore we show that fractionalization with similar
characteristics extends to the whole region corresponding to a repulsive LL.
