Introduction: Numerous factors influence the quantity and quality of saffron. Climate and temperature are important factors in determining the time of the initial irrigation  Applying the initial irrigation at the appropriate time in each area enables the management of flowers in terms of earlier emergence than leaves, while also increasing the quantity and quality of the product and lowering harvest costs. The timing of the initial irrigation was critical for the corms to awaken. Nutrient availability, particularly microelements such as iron and zinc, is another critical factor in saffron cultivation. Iron is required for chlorophyll synthesis, while zinc is required for chlorophyll, carbohydrates, and tryptophan synthesis. Chelate micronutrients, according to researchers, are more effective than conventional compounds. The purpose of this study was to determine the response of saffron's morphophysiological characteristics to the first date of irrigation and the application of iron and zinc fertilizers in chelate and Nano-chelate forms.
Materials and Methods: This experiment was conducted in Faraman Dorod village of Kermanshah province in 2016-2017 to determine the effect of first irrigation time and chelate and Nano-chelate forms of iron and zinc fertilizers on the morpho-physiological characteristics of saffron. Split plots were used in a randomized complete block design with three replications. The first irrigation time was on November 31 Oct, 10 and 20 Nov as main plots, and chelate and Nano-chelate fertilizers were included as subplots in levels (F1, F2, and F3 at 4, 8, and 12 kg.ha^-1 from iron and zinc chelate fertilizers, respectively, as well as F4, F5, and F6 at rates of 4, 8, and 12 kg.ha^-1 from iron and zinc Nano-chelate fertilizers, respectively, and control (F0, without fertilizer)). SAS software, version 9.1, was used to conduct analysis of variance on the data. The Duncan test indicates that the means in each column that has at least one letter are not significantly different at the 5% probability level.
Results and Discussion: The results revealed that the first irrigation date and fertilizer had a significant impact on the number of leaves per plant, flower dry weight, stigma dry weight, crocin, picrocrocin, and chlorophylls a and b. The application of the first irrigation on 10 October resulted in the highest dry weight of flowers (0.48 g.m^-2) by approximately 14.29 percent compared to the application of the first irrigation on 30 October. Under the influence of fertilizer, the application of 12 kg.ha^-1 of iron and zinc Nano-chelates produced the highest flower dry weight. The application of fertilizer decreased the amount of proline, with 12 kg/ha of nano-iron and nano-zinc chelates producing the lowest levels. Under the influence of the interaction between the date of the first irrigation and the type of fertilizer, significant differences were observed between the examined treatments. According to the results, the dry weight of stigma and safranal increased with earlier irrigation dates, and the highest dry weight of stigma (236.96 mg.m^-2) was obtained by applying 8 kg.ha^-1 of nano-iron chelate and zinc with the first irrigation on 10 November. The highest dry weight of stigma increased by 47.56 percent when compared to the initial irrigation treatment on 30 November and no fertilizer application (160.59 mg.m^-2).
Conclusion: The results showed that to obtain maximum stigma yield, 1st of November for first irrigation and the application of 12 kg.ha^-1 of chelate or 8 kg.ha^-1 of Nano-chelate is suitable.