Base on the studies of Pumijumnong and Arunrat (2012; 2013) and Arunrat and Pumijumnong (2014) and Arunrat
et al., (2014). The assumptions for the simulation are as follows; (1) the cropping calendar is fixed, (2) crop
management is fixed (rice variety, fertilizer, pesticide and herbicide), (3) each simulation unit (SU) with similar
environmental conditions (topology, soil property and weather data), (4) the climatic variables directly affect
crop yields, (5) all parameters are fixed, and (6) current trade policy is not changed. We used the essential data
and information for i-EPIC Model includes: