Evaluation of the effects of some biofertilizers on nutrient uptake and essential oil yield in the golden plant (Dracocephalum kotschyi Boiss) under different soil moisture regimes

Dracocephalum kotschyi is one of the most important medicinal plants of the family Lamiaceae which is endangered due to unfavorable environmental conditions. Therefore, in order to investigate the effect of biofertilizers at four levels (nitroxin, super nitroplus, biophosphorus and non-use of biofertilizer) on essential oil yield and nutrient uptake of D. kotschyi seedlings under drought stress at three levels (irrigation to completion 80, 60 and 40% of field capacity) a completely randomized design in 3 replication (each replication includes 25 pots containing one seedling) was performed in the greenhouse as a pot experiment containing cocopeat and perlite culture medium in a ratio of 1: 1. The highest amount of root nitrogen uptake (2.2 mg kg-1) and leaf nitrogen (57.5 mg kg-1) was observed in conventional irrigation treatment (irrigation treatment up to 80% of field capacity) and application of super nitroplus biofertilizer. The percentage of essential oil under mild stress increased by 77.53% compared to the control, while with the intensification of drought stress, the percentage of essential oil decreased by 94.49% compared to the control. The results of this study showed that the most increasing effect on essential oil percentage (1.1%) and essential oil yield (1.5 g plant-1) of D. kotschyi was related to inoculation with Super Nitroplus biofertilizer and mild drought stress, while cultivation of D. kotschyi under normal irrigation conditions and no biofertilizer resulted in the lowest production and yield of essential oil.