نوع مقاله : مقاله پژوهشی
1 دانشکده جغرافیا دانشگاه تهران
2 دانشکده جغرافیا، دانشگاه تهران
3 پژوهشکده هواشناسی
عنوان مقاله [English]
Consideration to climate variables are the primary factors that controlling rainfed cultivation and the adaptation of the growing and reproductive period to the appropriate climate conditions provide through the sowing date. Therefore, the main objective of this research is to offer the time of the occurrence of water stress susceptible stages (flowering and milking) in order to achieve optimal yield in the main areas of rainfed wheat cultivation in Iran. Six western and northwest provinces of Iran are the first to sixth- largest in terms of area under cultivation and yield in rainfed wheat production, in this regard, it was used daily statistics of temperature and precipitation during (1998-2014) as well as soil texture data were used which had the appropriate coverage of the studied area (31 Stations).Firstly, it was offered a new definition of effective precipitation and determined sowing date and germination. Then, considering the degree-day of growth (1400-1700), the date of the beginning and the end of the flowering and milking stage was determined. The calculations were performed with SMADA software at three probability levels: 70, 80 and 90 percent, with choosing of the best statistical distribution. Accordingly, it was determined the time interval from 23 September to 27 October for germination and 2 periods between March 15th and April 15th and May 10th to June 10th for flowering and dying periods.