Changes in Yield and Essential Oil Compositions of Dracocephalum kotschyi Boiss in Response to Azocompost, Vermicompost, Nitroxin, and Urea Under Water Deficit Stress

Dracocephalum kotschyi Boiss has safe anticancer properties, and is regarded as an endangered plant in Iran. The indiscriminate use of chemical fertilizers and the resulting environmental damages made it essential to shift to utilizing organic fertilizers and soil amendments for increasing the water and fertilizer efficiency in sustainable agriculture. This study aimed to investigate the changes in yield and essential oil compositions of Dracocephalum kotschyi in response to azocompost, vermicompost, nitroxin, and urea under different irrigation regimes. To investigate the effects of both nutrient inputs and water availability on yield and essential oil composition of D. kotschyi, at a semiarid site of Iran, a split-plot experiment was conducted based on a randomized complete block design with three replications in 2018–2019. The main plots were four irrigation regimes including irrigation up to field capacity after depletion of 20% (unstressed control), 40% (mild stress), 60% (moderate stress), and 80% (severe stress) soil available water. The subplots consisted of unfertilized control and four fertilizer sources (urea, nitroxin, vermicompost, and azocompost). The highest biomass was observed through vermicompost application in unstressed treatment at the third harvest (4058.9 kg ha−1). Moreover, the highest essential oil content was obtained under water deficit stress in the first harvest. The highest essential oil yield was also produced with application of vermicompost (40.90 kg ha−1) and azocompost (40.42 kg ha−1) under unstressed conditions at the third harvest. In harvest summations, urea fertilizer had the highest essential oil yield under unstressed control (75.19 kg ha−1), mild (64.79 kg ha−1), and severe (65.63 kg ha−1) stress conditions, while it was produced from nitroxin treatment under moderate stress (53.63 kg ha−1). Geraniol, dl-limonene, cis-sabinene hydrate, neral, geranial, methyl geranate, and geranyl acetate were the main components of the essential oil profile. D. kotschyi showed different responses to water availability in conjunction with various fertilizer sources. Therefore, we can say that it tries to make better response to different conditions for its survival and development by changing essential oil content and compounds. Our findings suggest that organic fertilizers, especially vermicompost, can improve soil properties and essential oil yield. Finally, based on the results of this study, urea is recommended for unstressed, mild, and severe water stress conditions, and nitroxin for moderate conditions.