In order to investigate the effective factors on the reduction of rain-fed wheat yield, an experiment in 45 fields was conducted in the township of Bandar-Gaz in 2012. In this research, all information such as crop management operations, seedbed preparation, cultivar, site preparation, seed sowing, weed combating, planting and harvesting issues, time of toxicant spraying, used seed rate were collected during a growing season by preparing questionnaire answered by farmers. In addition, at the end of the growing season, the actual yield harvested by farmers, were recorded. Among the various parameters, plant and raceme density, farmer experiment, planting and harvesting dates had significant effects on wheat yield. Farmers with higher experiment had lower yield and with delay in planting and harvesting, yield was reduce. Results showed, there was between actual yield mean (2236kg/ha) and attainable yield (5698 kg/ha), 3462 kg/ha yield gap due: low plant density (15%), lack of acceptance of new finding (10%), late planting date (30%), inappropriate cultivar N8019 compared with N8118 (21%), non-use Topic and Geranestar herbicides(18%).
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