SIMULATION MODELING OF LAND SUITABILITY EVALUATION FOR DRY SEASON PEANUT CROPPING BASED ON WATER AVAILABILITY IN NORTHEAST THAILAND - EVALUATION OF THE MACROS CROP MODEL

The MACROS crop model was evaluated for its utility to generate inform ation on land suitability for dry season peanut cropping based on wate r availability at the regional scale in Khon Kaen Province, Northeast Thailand. The model was specific for the condition where crop growth i s limited by water stress, and evaluated using both calibration and va lidation phases in sequence. In the model calibration, data sets from one peanut field experiment were used to calibrate some parameters to obtain the best agreement between experimental and simulated results. The model validation, in this study consisted of a 'validation A', wit h emphasis on the accuracy and a 'validation B', with emphasis on the usefulness and relevance of the model. In the model validation A, data sets from peanut field experiments were used to validate the model un der different conditions. Satisfactory agreements were found between t he dynamics of observed and corresponding simulated values of shoot dr y weight in every condition involved in this validation study. Also th e simulated pod yields agree well with the field data. For the validat ion B, the model was further validated using data from 36 farm trials conducted at 5 different test sites. A high positive correlation (r = 0.91) existed between observed and simulated pod yields. Because of th ese satisfactory agreements between observed and corresponding simulat ed values, it was concluded that the model is valid and can be applied to Khon Kaen Province.