Evaluation of growth, yield, and physiological responses of Valeriana officinalis L. to the application of urea, nitroxin, and phosphate Barvar-2 fertilizers

In the study, to survey the growth, yield, and physiological responses of valerian (Valeriana officinalis L.) using different concentrations of urea fertilizer (0, 30, 60, 90, and 150 kg.ha-1) and nitroxin and phosphate Barvar-2 bio-fertilizers, an experiment was conducted in medicinal Plants farm, Tehran, as a factorial in a randomized complete block design with three replications in the 2019-2020 crop year. Seedling cultivation was carried out in mid-May and urea fertilizer treatment was performed in two stages. To measure root and biological yield, one square meter was harvested from each plot and the dry weight of shoot and root was measured and the sum of these two was calculated as biological yield. Root and rhizome essential oils were extracted by water distillation (Clevenger) and valerenic acid by high performance liquid chromatography (HPLC). Essential oil yield was also calculated based on the essential oil percentage and dry root yield. The average root diameter varied from 7.97 (90 kg urea per ha) to 5.14 mm (control). The highest root yield was obtained in 150 and 90 kg urea.ha-1 along with inoculation with nitroxin and phosphate Barvar-2 (4.88 and 5.1 ton.ha-1, respectively). Application of 90 kg urea.ha-1 along with nitroxin resulted in increased chlorophyll b and total content. Increasing the urea concentration decreased essential oil content and increased essential oil yield. Essential oil content ranged from 0.93 (90 kg urea.ha-1 with nitroxin and phosphate Barvar-2) to 1.94% (no-application of fertilizers). The highest valerenic acid content (0.46% of the extract) and valerenic acid yield (220.27 mg.ha-1) were observed using 30 kg of urea with phosphate Barvar-2 and no application of nitroxin. In general, application of nitroxin and phosphate Barvar-2 bio-fertilizers along with 90 kg urea.ha-1 by improving growth, yield, and physiological traits led to the production of acceptable essential oil and valerenic acid yield.