The objective was to evaluate the decomposition and nutrient release of biomass from maintenance of fallow or oat crop (IPR 126), managed in integrated crop-livestock, during the soybean crop cycle (85 days) in no tillage system in two years (2014 and 2015). The design was a randomized complete block in a subdivided plot scheme, with the parcel consisting of four plots (four straws, from fallow or oat cultivation) and the subplots (evaluation periods 0, 10, 35, 60 and 85 DAS) with the evaluation times throughout the crop cultivation soybean. The amount of biomass and the content of C, N, P, K, Ca, Mg and Zn were calculated. The amount of biomass and nutrients presents a similar pattern of decrease in their values; however, the climatic conditions and the C/N ratio play an important role in the decomposition and mineralization of nutrients. The mineralized amount of N, K, P, Ca, Mg and Zn is directly proportional to their initial content in the biomass, and K nutrient is quickly released from crop residues. Most of the nutrients studied were released during the soybean crop development cycle, favoring its development; this can provide a reduction of external inputs in the property.