Spatial distribution and deviation from optimum temperature conditions of phenological stages of potato cultivation in West Azerbaijan

The study occurrence time of the phenological stages of agricultural products based on thermal conditions is important. In this study, firstly the relationship between climatic parameters and potato yield was studied based on multivariate regression method. In the following, time of occurrence phonological stages, cropping calendar, and deviation from optimal temperature were determined based on daily temperature statistics from 1989 to 2014. Based on the thermal gradient between low and highlands, the temperature up to 3000 m was estimated. The results showed that there is a significant relationship between temperature components and potato yield. The topographic condition determined the completion time of the thermal units required for potato plant phenology phases. In the study area from the easterly areas to the rugged Western regions, the planting time of 1 month is delayed. The first and last phases of potato plants, called sprouting–leaf development and flowering–ripening, require the smallest and most effective thermal units, respectively. For the sprouting, leaf development, inflorescence emergence, and ripening were 437, 692, 540, and 1126, growth degree days, respectively, required. Estimation of air temperature based on the least-squares regression showed that for the 1000 m height, 1 month of optimum temperature of potato cultivation was delayed. In low and highlands of the region, the planting and harvesting, respectively, occurred in May–June and August–October, respectively. Matching the phonological stages of each product’s growth with thermal conditions in geographical information system is effective for planning in irrigation, spraying, and other agronomic activities.