Introduction: The barely (Hurdium vulgare L.) is one of the oldest cultivated plants and that is one of the most important cereals in Iran after wheat in terms of production and cultivated area. One of the main problems of barely production in the eastern region of Golestan province, Iran is considerable difference between actual yield and attainable yield which is called yield gap. In recent years, this gap has been impressive, which decreasing the gap between actual and potential yield (maximum production which can be achieved by proper management), requires detailed study and analysis of its causes. Therefore, identifying barely yield-limiting factors are essentially needed. Therefore, the present study was conducted in Kalaleh in the eastern region of Golestan province, Iran for simultaneous recognition of best management practices, percentage of the affected fields, estimation of barely yield potential and gaps using the Comparative Performance Analysis (CPA) method.
Materials and Methods: Therefore, identifying barely yield-limiting factors are essentially needed. Inorder to this study was conducted to evaluate the factors limiting barely yield in Kalaleh in the eastern region of Golestan province using the Comparative Performance Analysis (CPA) method in 2020-2021. Collection of the required information (such as planting date, holding and harvesting activities, soil physicochemical properties) was done by fieldwork, and personal interviews with farmers. To this aim, 38 barely fields in geographical location of the study area were monitored in each crop year. In the comparative performance analysis (CPA) method, using stepwise regression, the relationship between variables and yield were considered. And yield gap rate, its causes factors and it was also estimated the contribution of each of these factors to the creation of a yield gap.
Results and Discussion: Among the investigated variables, the model (final regression equation) with four independent variables was selected (nitrogen fertilization frequency, amount of phosphorus fertilization, frequency of fungicide use and frequency of pesticides).The results of yield model showed that there was a difference of 1253 kg/ha between attainable (5063 kg/ha) and actual yield (3810 kg/ha). Among studied variable, nitrogen fertilization frequency, amount of phosphorus fertilization, frequency of fungicide use and frequency of pesticide use with 29, 22.6, 24.2 and 24.2% respectively, had the most influence on barely yield gap in the study area. The results showed that the number of times of fertilization caused 363.8 kg/ha of yield gap. Every plant needs the right time for fertilization for more yield. If the best fertilization time is not chosen for the plant, later or earlier fertilization will cause harmful effects in the plant. The amount of phosphorus consumed was the factor that had the least contribution to the limitation of barley yield in the studied fields (828.8 kg/ha). Phosphorus nitrogen affects root growth, and helps absorption of nutrients by plant, balances nitrogen deficiency in the soil. The results showed that frequency of fungicide use caused 302.8 kg/ha of yield loss. In other words, by using fungicide twice during the crop growing season, barley yield increased by 302.8 kg/ha. Also, the effect of frequency of pesticide use on the yield gap was similar to frequency of fungicide use. Therefore, farmers should consider weed control as an important factor in increasing the yield of this crop.
Conclusion: In this study by examining four important management factors in growing barely, optimal requirements of each factor to achieve the highest yield was determined by CPA. Inorder to with proper and principled agricultural management and modification of the influencing factors, the difference between the attainable yield and the actual yield can be reduced and the desired result can be achieved.