Direct-seeding mulch-based cropping systems (DMC) are known to have multiple effects on soil biotic and abiotic properties such as an increase in soil C and N, a reduction of surface water runoff and when there is no cover crop, an increase in drained water below the root zone. In Brazil, where direct-seeding is practiced by large-scale mechanized farmers, DMC systems including a cover crop before or after the main commercial crop present an opportunity to improve the durability of this practice, notably to reduce the use of chemical N fertilizers. Maltas et al. (2009) showed strong inter-annual variability in N losses under DMC systems during the growing season of the main crop that is likely to be linked to inter-annual variations in rainfall patterns. In order to provide recommendations to farmers for a more efficient N fertilisation management of the main crop along with the choice of the cover crop, a better understanding of the N cycling is needed. That can be reached through simulations based on soil-crop model which are able to account for water and N dynamics under DMC. The objective of this study is to calibrate the crop model STICS (Brisson et al., 2009) for the Cerrado region (Brazil). We present modifications of the model and calibration of the soil-plant parameters linked to N dynamics using the data coming from maize plots without a cover crop and without N fertilisation.