simulation of economic damage at mechanized wheat harvesting in khuzestan province of iran

The aim of this research is to present a simulation model for reducing economic damages of mechanized wheat harvesting in the weather conditions of khuzestan province and similar areas. the simulated model is composed of three submodels, for determining of the appropriate working hours, grain losses, and economic submodel. in order to determine the appropriate working hours, a mathematical model was devised. for determining the grain losses, 52 fields in hamidieh, a small town in southwest of iran were selected. several mathematical models were developed for predicting the natural cutting platform and combine end losses plus the percentage of broken seed. the average appropriate working hours was obtained by a computer simulation model based on meteorological information of an 8 year period.  the maximum acceptable speed for two the combines, 955 john deere and tc56, was 2.5 and 4 km per hours, respectively.  a minimum grain loss happened in 4 days after physiological maturity and the best time range for wheat harvesting in khuzestan was 2 to 15 days after physiological maturity. at the beginning of the harvest season the combine loss in the early hours of day, due to high moisture of crop, was more than the midday time or afternoon. however, after 10 days of physiological maturity, the reverse happened. results showed that despite the growing cost of delay in harvesting, no matter how vast the fields are it will not justify combine ownership; thus employing rental combines is more costeffective in fields of any size in khuzestan.