Intercropping and nitrogen fertilizer enhance essential oil quality in Dracocephalum kotschyi Boiss

Abstract

In recent years, there has been an increasing interest in medicinal plants and their products due to the importance of herbal medicines in the global market. The chemical composition of D. kotschyi has not been studied in relation to intercropping and nitrogen effects. This study aims to analyze the chemical composition of D. kotschyi essential oil under different intercropping patterns and nitrogen applications. In addition, this research focuses on the effects of legume residues on the chemical composition of essential oil and compares it with nitrogen treatments. The experiment was conducted in a randomized complete block design with three replicates in 2018 and 2019. The experimental treatments included an additive intercropping of green bean (G:D), common bean (C:D), soybean (S:D), and mung bean (M:D) at 20 % of their optimal density with D. kotschyi. The fertilizer treatments included D. kotschyi sole cropping in combination with different nitrogen applications: 0 (control), 40, 80, and 120 kg N/ha. The main results are: The G:D treatment yielded the highest essential oil. Alpha-pinene and dl-limonene levels increased with higher nitrogen fertilization across all harvests. M:D treatment exhibited peak levels of neral, geranial, and geranyl acetate. Among different legume residues, G:D produced the highest alpha-pinene, while D:N120 had the highest dl-limonene. Geranial and geranyl acetate levels were highest at D:N40 and D:N80, respectively. These results suggest that D. kotschyi can be cultivated by either intercropping with green bean at 20 % of the optimal density or with legume residues or sole-cropping with nitrogen fertilizer. The contribution of this study was to confirm that the chemical compounds of the essential oil of this plant can be improved by cultivation methods and nitrogen management.