Evaluation the impact Climatic parameters on flowering behaviour and yield of Saffron (Crocus sativus L.) in Razavi and Southern Khorasan Provinces

In order to evaluate the trend of saffron yield and study the relationship between saffron yield fluctuations and various climatic parameters, research was designed and conducted in Mashhad, Torbat Heydariyeh, Kashmar, Birjand and Qaen during 20 years (1998-2018). According to meteorological data from the last 20 years, the average rainfall decreased by 33% and the average temperature increased by 0.5 °C . On the other hand, the regression results between yield and climatic parameters indicates that the pattern of temperature rise and decreased rainfall in all studied cities was significantly in line with saffron yield declining. In this period, the study's findings also revealed that over the last 20 years, an average of 112.3 hectares of saffron cultivation have been added to the areas under cultivation of saffron and at the same time, saffron yields have dropped by an average of 0.08 kg per hectare. Climatic indicators significantly affected decreased saffron yield in Razavi and South Khorasan. The results also revealed that the average and maximum temperature were the main variables influencing the reduction of saffron yield. For instance in Torbat-e Heydarieh, the variable of average temperature predicted 42 percent of the variability of the yield and in other cities studied, the maximum temperature variable predicted between 24 and 56% of the variability of the yield. Furthermore, the results of the time series analysis of saffron yield revealed that saffron yield will show a decreasing and negative trend by 2025 in all studied cities. Up to 2025, Mashhad and Kashmar with a slope of 0.09 and 0.07 kg/ha, had the highest and lowest decreasing trends, respectively.