Chromolaena odorata, a wild species, and Pueraria phaseoloides, an introduced species, were compared as fallow plants over 6 and 18 month periods, in a permanent annual sequence with a 4-month maize (Zea mais) cropping cycle. On average, P. phaseoloides restored more N than C. odorata (145 kg ha-1 compared to 87 for 6-month fallows, and 245 kg ha-1 compared to 178 for 18-month fallows). Short-term P. phaseoloides fallows promoted nitrogen mineralization by soil and N uptake (N export from grain maize, restoration via maize mulch). Cropping systems with 18- month live fallowed plant cover were not more productive than the slash-and-burn control with C. odorata cover. After 4 years, organic N supplies in the surface horizon declined for systems with 6-month fallows, and were generally higher with C. odorata cover.