Aims Root respiration is a major contributor to soil CO2 flux, and its response to management practices needs to be evaluated. The aim was to determine the effect of management practices (tillage systems and nitrogen fertilization levels) on root respiration and to develop a model able to simulate root respiration and its components. Methods The study was carried out during two contrasting growing seasons (2007–2008 and 2008– 2009). Root respiration, including root tissue respiration (Rts) and rhizomicrobial respiration of exudates (Rrz), was estimated as the difference between the soil CO2 flux of cropped and bare soil (the so-called root exclusion technique). Additionally a novel sub-model of Rts, was used to simulate root respiration based on root growth and specific root respiration rates. Results Root respiration was reduced under notillage. The model agreed well with the patterns and the amounts of the observed values of root respiration, although prior calibration was needed. Conclusions Root respiration was reduced by the long-term adoption of no-tillage, but was increased by N fertilizer. The root exclusion technique and the model were useful means to estimate root respiration on cropland under semiarid Mediterranean conditions. Additionally the model successfully separated out the theoretical contributions of Rts and Rrz to root respiration.