This research aims to study the kinetics of N mineralization by using double-pool kinetics models on degradated soils in the cultivation of monoculture cassava as a result of providing organic matter of legume and non-legume. Incubation experiments were conducted in the laboratory at a constant temperature. The treatment was by giving nonlegume and legume biomass on Ultisol in which cassava has been planted there with different lengths of time. In this research, to estimate the parameters of the mineralized N and the rate of mineralization (k), double-pool kinetics equation was used. Mean while, the relationship between the parameters of N mineralization with nutrient uptake was investigated by conducting a pot experiment in a greenhouse. The results showed that the application of organic matter derived from groundnut produced higher mineralization. The N mineralization of soil that has been planted by cassava less than ten years was higher than it was on soil that has been planted by cassava more than 30 years. The total amount of N released on soil that has been planted by cassava less than 10 years reached 1086 mg kg -1. Whereas, the total amount of N released on soil already planted with cassava more than 30 years was 783 mg kg -1. Potential value of N (N0) and the mineralization rate coefficient (k) were higher in organic matter with a low ratio of C:N and on more fertile soil.
