study for zoning the most appropriate time of irrigation of saffron (crocus sativus) in khorasan razavi, north and southern provinces

abstract saffron (crocus sativus, l.) is one of the most important economical crops for khorasan farmers. almost all saffron yield in iran comes from khorasan provinces. first irrigation times is the crucial factors which affect the amount and quality of yield based upon an on farm investigation it was found that when air temperature reaches to 12 ۫c the most amount of flower is yielded. also it was found that 2 to 3 weeks after irrigation flowering starts. the one irrigation should be applied in such a way that after this period of time saffron could be harvested. in this study the most appropriate date for the time of irrigation with 50, 75 and 95% probability was derived for different points of khorasan provinces. also khorasan provinces were zoning for this purpose. based on results, flowering date and first irrigation time for saffron are very different and depended on climate and temperature of studied zone. in the locations with higher elevation above the sea level and lower daily air mean temperature, usually flowering date and first irrigation time are very soon in the autumn early while decreasing of elevation above the sea level and increasing of daily air mean temperature, flowering date and first irrigation time are in the mid autumn or even autumn late.