technical and economical evaluations of canola harvesting losses in different maturity stages using three different combine harverster heads

rapeseed cultivation in iran is growing rapidly while this product has been facing specific problems. every year a significant portion of edible oil is imported to the country from other countries. despite this deficit, a great amount of canola is being lost every year. therefore, in compliance with technical points, adding a suitable platform to the exisiting machineries may reduce the losses. a field study was conducted in moghan agricultural research centre to study the technical and economical characteristics of harvesting machineries and evaluate canola harvesting losses in different maturity stages, using three different combine harvester heads. the experiments were conducted in a completely randomized split split plot design with four replications. the main plot included seed maturity stage at three levels: a) 60%, b) 70% and c) 80%, and the subplot was the harvester’s ground speed at three levels: a) 1.5, b) 2.5 and c) 3.5 km h-1. the sub-subplot was combine head type with three forms: a) mechanical, b) hydraulically joybar and c) hydraulically biso's head. the results of anova showed that maximum cutter bar losses occurred with mechanical head (5.36%) while the loss of hydraulically joybar's and biso's head were 4.28 and 4.13 %, respectively. the results also showed that the maximum cutter bar losses occurred when 80% of seeds were matured and adequate time for canola harvesting was 70% of seeds maturity. the results of analysing the effects of harvesting ground speeds showed that the maximum cutter bar losses occurred with the speed of 3.5 km h-1. finally, the results showed that the minimum cutter bar loss was obtained with hydraulically joybar's head considering the benefit per cost ratio. the cost for mechanical head and hydraulically biso's head were 13500 and 262500 rial ha-1, respectively.