Zoning the Length of Growing Period based on Temperature Characteristics in Iran

1- Introduction Length of Growing period (LGP) is a time in which sufficient moisture and a lack of thermal restrictions enables the production of crops. Among the climatic elements, temperature is an important factor and consequently, the study the effect of temperature on the growth of organisms, especially plants, is necessary. Many of the products planted traditionally are not benefited from favorable climatic factor. Accordingly, on one hand, reduce crop yield and on the other hand, They led to the improper use of climate capability production. The role of temperature on the growth of plants and animals are clearly known. Temperature range for each areas are the plant species and crops index according to that farmers could grow crops. Identifying and selection crops adapted to temperature of the region can be expanded various agricultural system until Risk of damage production due to natural changes temperature reduce. If temperature reaches below the critical level of growth, plants’ growing stages will stop. This may hurt plants. It appears that the process of global warming that causes LGP in Iran has changed 2- Theoretical framework Determining the growing season in each region has a huge role in crop selection, the variety and timing of crop planting and other decisions. The purposes of this research are to analysis and classify the LGP by base temperatures 5 and 10 with the minimum daily temperatures between 1987-1988 and 2007-2008. 3- Methodology In this research, the data from minimum daily temperature from 31 Iranian synoptic stations during 20 years have been analyzed from 1987-1988 till 2006-2007. LGP for two thresholds of 5 and 10 ° C were determined and the beginning and the end of the threshold for the aforementioned temperatures with Julius coding (January 21, with first code and January 20 in next year is last cod) were calculated. In this research, the beginning of LGP is the first 6 day period with Tmin≥ 5 and Tmin ≥ 10. The end of LGP is the last 6 day period with the Tmin 350 days. For temperature 10 C° the same number of groups were seen including 50-100, 100-150, 150-200, 200-250, 250 -365 days. 5- Conclusion and suggestions The Zoning of LGP based on temperature 5 and 10 C thresholds in Iran showed that the beginning of 5 and 10 ° C is earlier in south areas of the country and is late in the northern and western areas. In Northern areas, the beginning of LGP is earlier than the western areas due to temperature and humidity. The zoning end of LGP reveals that in western areas, the end of LGP is earlier than other regions due to lower temperatures and in southern and northern areas, the end of growing season period is longer. The results showed that LGP decreases from south to west and west-north so that based on the base temperature threshold, Bandara Abas station has the longest LGP and Shahrekord has the lowest compared to other stations. Growing season length of 5 were divided into five categories The first group consists of stations located in mountainous regions of the country, including 150-200 days. And the second group of stations located in the North East, Central and West cities of Country includes 200-250 days. The third group consists of Tehran, Zahedan, Shiraz, Gorgan, Yazd with 250-300 days. The fourth group consists of the northern cities and the Bam are 300 to 350 days. Finally, the fifth group consists of the southern cities with more than 350 days during the growing season. Growing season lengths of 10 were divided into five categories. First group consists of Hamadan and Shahrekord with 50-100 days. The second group consists of cold towns with 100-150 days. The third groups of growing season length are between 150-200 days, including the cities of Isfahan, Birjand, Tabriz, Tehran and Zahedan, Sabzevar, Shiraz, Qom, Mashhad and Yasooj. The fourth group consists of the northern cities, Tehran and Yazd with 200-250 days. The fifth group includes southern tropical cities with growing season lengths, 250-365 days. In general, accurate knowledge of length, the beginning and the end of the growing season period for plants in 5 & 10 C base temperature will be useful for agricultural planning, planting and harvesting crops, Selecting species are compatible with the threshold temperature and in addition to the condition of the areas..