The effect of long-term fluctuations in temperature and rainfall on saffron yield

According to the findings of this research, the decrease in saffron yield in Khorasan province during the last 10 years is significantly affected by the changes in weather indicators, especially temperature and humidity, so that among the main saffron-producing cities of the province, the yield changes range from 31 to 66 percent. It can be described with these climate variables. In this research, among the meteorological parameters, the effect of rainfall was less compared to the monthly temperature, and the results showed that rainfall has a significant role only in one of the main cities of saffron production, Torbat Heydarieh, while the minimum and maximum monthly temperature The main variables affecting the reduction of saffron yield are considered, and it was concluded that the temperatures of spring months (April, May and June) and to some extent the first months of summer (July) show the most negative effect on saffron yield. The pattern of increasing minimum and maximum temperatures of these months in the saffron producing cities in Khorasan province during the last 10 years has shown a significant adaptation to the trend of decreasing saffron yield during this period. Based on this, the spatial-temporal patterns of changes in saffron yield (along with other effective agronomic, managerial and economic variables) are also subject to climate changes and it seems that with the continuation of climate changes, saffron yield will continue to decrease in the coming years. will give.

The effect of climate has been identified in many parts of the world for different crops. This effect is related to the three factors of atmospheric CO2 concentration, rainfall and temperature.
The results of the research on the relationship between meteorological data and the yield and cultivated area of ​​agricultural plants show that changes in temperature and rainfall affect the yield of agricultural plants so that the average yield of agricultural plants increases with more rainfall and vice versa decreases with higher temperatures, or in other words In other words, the increase in rainfall causes a decrease in the variability of the yield of plants and an increase in temperature causes an increase in the variability of the yield of agricultural plants.
The temperature factor is of special importance at least monthly in the months that coincide with the appearance of flowers in saffron. The mechanism of flowering in saffron is such that the more the temperature drops at night, the more flowers will appear the next day, and the areas where the temperature drops earlier are ahead in terms of flowering. The coefficient of variation of monthly rainfall during the year shows different values ​​in different stations and the maximum value of the coefficient of variation is in the months of the autumn season which is the rainiest time of the region and the minimum occurs in the summer.
Studies on a global scale have shown that future climate changes by affecting the amount of temperature and rainfall will affect the agricultural potential in different regions by changing the length of the growing season. Researches have shown that the length of the growing season was calculated based on the combination of temperatures above zero and the availability of moisture for plant growth. The presented values ​​indicate the shortening of the length of the growing season in arid and semi-arid regions of the world, including Iran, while In high latitudes, the length of the growing season will increase in the future.
The increase in the probability of extreme phenomena in arid and semi-arid regions of the world will greatly limit the conditions for agricultural production in these regions. The evidence indicates that in the climate change conditions, the lack of water (rainfall) will be the main limitation of grain production in these places.
The increase of greenhouse gases in the atmosphere and its consequences, such as global warming, will have significant effects on the world’s agriculture by affecting the amount of annual rainfall. Despite the importance of these effects, there are few studies and researches conducted in this field in developed countries and regional studies regarding the impact of climate on agricultural production in developing countries.
On the other hand, most of the arid and semi-arid regions of the world, which are more sensitive to climate change due to their ecological structure, are located in developing countries. Population increase, reliance on agricultural products and lack of sufficient information about future climate conditions, together, threaten the future food security of the residents of these areas. Based on this, extensive research on the consequences of climate change in a regional manner in order to achieve the future vision and adopt appropriate solutions to deal with it is considered a research necessity in these countries.
Therefore, considering the effect of climate changes on crop yield, the long-term trend of yield of these crops, which is based on common statistical methods, can be a suitable solution to determine the contribution of climate factors on yield fluctuations, and since this trend of yield changes of crop plants in Regional and national scales have been studied in many parts of the world, so it was necessary to conduct such studies in Iran. For this purpose, considering the economic and social importance of saffron for Khorasan province and the country, evaluating the trend of saffron performance in recent years and studying the relationship between its fluctuations and climate changes is the goal of this research.

According to the findings of this research, the decrease in saffron yield in Khorasan province during the last 10 years is significantly affected by the changes in weather indicators, especially temperature and humidity, so that among the main saffron-producing cities of the province, from 31 to 66 percent of yield changes can be described by these climate variables. In this research, among the meteorological parameters, the impact of rainfall was less compared to the monthly temperature, and the results showed that rainfall is the only