The effect of foliar application of different nano fertilizers on the quantitative and qualitative characteristics of peppermint (Mentha piperita L.) under water stress conditions

Materials and methods With the aim of investigating the effect of foliar application of different nano fertilizers on the quantitative and qualitative characteristics of peppermint under different irrigation conditions, an experimental experiment was carried out in an agricultural field in Miandoab city in West Azarbaijan province. The experiment was in the form of split plots based on randomized complete block design in three replications. The main plot was assigned to the irrigation cycle (every 5, 7 and 10 days) and the secondary plot was assigned to foliar spraying treatments (control (no foliar spraying) nano NPK, nano Fe, nano Zn and nano Mn). chlorophyll a, chlorophyll b, carotenoid, plant height, number of leaves per plant, leaf weight, fresh yield, dry yield, proline content, essential oil percentage and essential oil yield was measured. Results and discussion Based on the results of data variance analysis, all investigated traits were affected by irrigation, foliar application and the interaction of two treatments at the 1% probability level. The interaction of year with foliar application on dry and wet yield of fodder was significant at the probability level of 1%. The triple interaction of year × irrigation× foliar application and was significant only on proline content at the 1% probability level. The results of the mean comparison of irrigation with foliar application interaction treatments showed the Foliar application of nano Fe under irrigation conditions once every 5 days had the highest content of chlorophyll a, chlorophyll b and carotenoids (respectively with an average of 13.43, 3.61 and 4.12 mg g fresh weight-1), plant height (33.92 cm), leaf fresh weight (6.71 g), aerial fresh yield (13121 kg ha-1), aerial dry yield (4600.1 kg ha-1) and the lowest proline content (6.32 mmol g weight-1). Also, the highest percentage of essential oil (0.67%) was attributed to nano Fe foliar spraying under irrigation conditions of 7 days once. In this study, although the highest essential oil yield (24.74 kg ha-1) was assigned to the application of nano Zn under the irrigation once every 5 days' condition but there was no significant difference between the mentioned treatment and Foliar application nano NPK and nano-Fe in the irrigation treatment of 7 days' treatments. Conclusion It can be stated that the use of NPK and Fe in the form of nanoparticles under mild water stress conditions can improve the economic performance of the product and save water consumption. Also, foliar spraying of this fertilizer it was able to significantly increase the essential oil yield of in this plant under severe water stress conditions. Therefore, foliar spraying of nutritional elements in nano form can be a solution to improve the essential oil yield in peppermint plants under water stress conditions with different intensities.