study of primary tillage timeliness cost for irrigated wheat in fars province using system dynamics

delay in irrigated wheat primary tillage operations causes yield reduction and hidden timeliness cost in fars province. mechanization of primary tillage operations for irrigated wheat in fars province was simulated using system dynamics approach. a part of the model structure was related to the agricultural operations timeliness costs. for the mentioned simulation, causal relations between system components were known and the model was run based on time step of 0.125 of one year. the simulation results showed that the operations timeliness cost remained constant (approximately one million rials per hectare) from 2001 to 2004 in the province. the timeliness cost increased from 2004 to 2007 due to the non-uniform distribution of atmospheric precipitation and reached to 1211724 rials per hectare in 2007. the upward trend of this cost continued for the period of 2007 to 2010 because of using depreciated moldboard plows. the model predicted the amount of 2090511 rials per hectare for the timeliness cost in 2018. furthermore, it was found that reduction in the timeliness cost could be reached either by increasing the plowing speed by %30 in the permissible domain or increading the daily working hours by 4 hours.