One of the main problems of crop production in our country is the difference between the actual grain yield of farmers and the achievable grain yield or the yield gap. In order to investigate the management factors affecting the reduction of wheat yield in Mahdasht of Karaj, a field experiment was conducted in the crop year 2017-18 in the farms of Mahdasht which was previously selected by the researcher. In this study, using stepwise regression, the contribution of all management factors that may play a role in reducing yield has been investigated. The results of correlation between different factors showed a positive and significant correlation between grain yield with the number of irrigations, nitrogen application in the second stage, total nitrogen consumption during the growing period and micronutrient consumption at a probability level of 1%, and there was a positive and significant correlation with the area under cultivation at the 5% probability level. According to the recorded wheat grain yield values, the average actual wheat grain yield was 4775 kg.ha-1 and factors affecting yield reduction in this area including the number of irrigations (42%), area under cultivation (9%), previously cultivated crop (6%) and total nitrogen consumption (5%) were determined. Other management factors had little effect on grain yield reduction. Potential grain yield in Mahdasht of Karaj according to the regression model can be raised to 7630 kg.ha-1, and the grain yield gap in this area is 2860 kg.ha-1.
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