Assessing and modeling the role of the native legume Lupinus meridanus in fertility restoration in a heterogeneous mountain environment of the tropical Andes

► Lupinus meridanus, a paramo legume abundant in fallow plots, fixes 84% of its N. ► Its biomass peaks after 5 years fallow, but high variability exists between plots. ► Cumulated N2 fixed after 10 years of fallow oscillated between 0 and 23.5 g m−2. ► A stochastic succession model correctly simulated N2 fixation and its variability. ► Sowing the legume at the start of the fallow period can duplicate potato yield.