Some nuclear facilities have large tritium loads and subsequent environmental emissions and consequently, the radiological impact assessment is mandatory. In case of the unplanned (potential) accidents there are extremely large uncertainties of the model predictions for crop contamination and dose due to many factors affecting the Organically Bound Tritium (OBT) dynamics in crops. A full mechanistic model is difficult to develop due to the complexity of the processes involved in tritium transfer and the environmental conditions. The preparatory steps for a robust model are discussed in the present study, considering the role of the dry matter and photosynthesis contributing to the OBT dynamics in crops.