Modelling helps to understand the principal mechanisms affecting ecosystem functioning, and the causes of disturbances to them. They are essential for long term predictions and in making recommendations aimed at reducing harmful effects and preventing environmental disturbances (Ifremer, 2005).Many authors have demonstrated the benefits of using computer models in agriculture (Farage et al., 2005; Paul et al., 2003; Webb et al., 2003; Pumpanen et al., 2003; Qian et al. 2003; Parton, 1996; Smith et al., 1996, 1997). Although mechanistic soil-crop models are increasingly accepted as valuable tools in analysing agronomical or environmental issues potential users are faced with an equally increasing number of available models (Gabrielle et al., 2002; Plentinger and Penning de Vries, 1995; Farage et al., 2005; Paul et al., 2003; Webb et al., 2003; Pumpanen et al., 2003; Qian et al. 2003; Parton, 1996; Smith et al., 1996, 1997). In addition, little information is given as to the validity, limits and potential applications of these models, which would provide some guidance in the selection of the most appropriate package. As a result, models are chosen on the basis of practical criteria such as code accessibility or the existence of user-friendly interfaces rather than scientific assessment of their expected performance (Gabrielle et al., 2002). Again, although testing the models over long time-scales may not be possible in all cases, the description of processes in the model can be validated (Bente et al., 2004). The most important data for such research are long-term experiments with a duration of more than 20 years, with information available about SOM pool dynamics during the experimental period (Lyudmila et al., 2003). In this present work more than 35 years data were used which fits within the recommended range.Amongst the models that have been tested in various ecosystem and cropping system are the CENTURY 4.0, RothC, CERES, NCSOIL, SUNDIAL and STICS. These have been evaluated in the domain of carbon and nitrogen cycling and sequestration (Gabrielle et al., 2002; Plentinger and Penning de Vries, 1995; Farage et al., 2005; Paul et al., 2003; Webb et al., 2003; Pumpanen et al., 2003; Qian et al. 2003; Parton, 1996; Smith et al., 1996, 1997).RothC 26.3 model was developed with data from the long-term Broadbalk experiment at Rothamsted for monitoring the turnover of carbon in non-waterlogged topsoils that allows for the effects of soil type, temperature, moisture content and plant cover on the turnover process.