ABSTRACT
Climate characteristics, water balance parameters and yield of wheat vary substantially over years and soil conditions in Bulgaria. Agricultural practices, especially fertiliser use, modify water transfer and N-uptake associated with this crop and thus the risk of groundwater pollution. The objective of this paper is to test and adjust CERES-wheat model to the typical agricultural conditions in Bulgaria and afterwards to use it for risk assessment analysis under different situations. CERES-wheat model was calibrated during a trial in 1996/97 and validated during the following trial in 1997/98, under impermeable Vertisol soil conditions in Bojurishte (Sofia region). Two levels of nitrogen (0 and 200 kg N/ha) were applied. Water retention and conductivity data measured in laboratory and in the field were compared to literature and used to specify the soil parameters of the model (Fig. 1-left).
