Evaluation of nutritional status of saffron (Crocus sativus L.) in South Khorasan province by "Deviation from optimum percentage" (DOP) method

Balanced nutrition is one of the most important methods to increase the quantity and quality of agricultural products such as saffron. Optimal application of fertilizer and impose the balance between nutrients is very important; achieving it requires a proper assessment of plant needs. Because the leaf is the main and most important tissue of plant metabolism so decomposition of its nutrients and interpretation of the results according to standard methods can provide complete information about the nutritional status of the plant, and can also be used to determine the order of nutrient requirements and fertilizer priority of the fields. In the present study, in order to investigate the nutritional status of saffron in South Khorasan province, leaf samples were collected from 23 farms and analysed for determining the macro and micronutrients concentration. Using nutrients concentration in high yielding fields, reference concentration (Cref ) was obtained for N, P and K nutrients 2.94, 0.25 and 1.22 percent respectively. As well as Fe, Mn, Zn and Cu Cref was 215.17, 27.21, 21.30 and 7.27 mg/kg respectively. After obtaining the reference concentration, the DOP value was calculated and based on that, the order of nutrient requirements was determined. The results showed that the absolute value of DOP for all nutrients studied was more than zero, in the other words, there was a nutritional imbalance in all fields. In more than 95% of cases, the nutritional imbalance was due to nutrient deficiencies, although in a few cases, the nutritional imbalance was also related to the excess of nutrients. Based on the indices of deviation from optimum percentage, among macronutrients potassium in 70% of the studied farms and among the micronutrients, manganese in 60%, and iron in 30% of the farms, had highest negative indices. Overall and based on the results of this study, it can be recommended that in saffron farms of South Khorasan province, the use of fertilizers containing potassium, iron and manganese should be given priority.