Intercropping is one of the most important components of sustainable agriculture. The effects of chemical fertilizer (CF), arbuscular mycorrhizal fungi (AMF) (Glomus sp.) and AMF + nitrogen-fixing bacteria (NFB) including Azospirillum and Azotobacter (AMF + NFB) was studied on essential oil yield and compositions of Moldavian balm (Mb) (Dracocephalum moldavica L.) in sole cropping and intercropping with fenugreek (F) (Trigonella foenum-graecum L.). The experiment was conducted during 2020 and 2021 growing seasons in East Azarbayhan, Iran. The highest dry herbage yield (6132 kg ha−1) was obtained in Mb:F(4:2) and CF treatment. After sole Moldavian balm, the highest essential oil yield (15.28 kg ha−1) was obtained in Mb:F (4:2) and AMF + NFB treatment. Geranial, geranyl acetate, geraniol, neral, and nerol were the main chemical constituents of essential oil. In AMF + NFB treatments the geranial contents in intercropping patterns of Mb:F (1:1), (2:2) and (100:50), increased by 25.1, 15.5 and 34.6% compared with sole Moldavian balm. The highest LERT values were observed in Mb:F (100:50) cropping pattern in 2021 (1.70 and 1.63 for CF and AMF + NFB treatments). Generally, it can be concluded that Mb:F (100:50) intercropping and use of AMF + NFB bio-fertilizer could be recommended to medicinal plant growers in sustainable production systems.

Intercropping is one of the most important components of sustainable production of agricultural products. The effects of chemical fertilizer (CF), arbuscular mycorrhizal fungi (AMF) and the combination of AMF and bacteria (AMF + B) in sole Moldavian balm (Mb) (Dracocephalum moldavica L.) and intercropping with fenugreek (F) (Trigonella foenum-graecum L.), was studied on growth characteristics, essential oil yield and compositions of Moldavian balm. The highest dry herbage yield (6132 kg ha− 1) was obtained in Mb:F(4:2) cropping pattern and CF treatment. The highest values of essential oil content were observed in the Mb:F (2:2) cropping pattern (0.261%) and AMF + B treatment (0.259%). After sole-Moldavian balm, the highest essential oil yield (15.28 kg ha− 1) was obtained in Mb:F (4:2) cropping pattern and AMF + B treatment. Geranial, geranyl acetate, geraniol, neral, and nerol were the main chemical constituents of essential oil. In CF and AMF + B treatments the geranial contents in intercropping patterns of Mb:F (1:1), (2:2) and (100:50), were greater than that of sole-Moldavian balm. The highest LERT values were observed in Mb:F (100:50) cropping pattern in 2021 (1.70 and 1.63 for CF and AMF + B treatments). Generally, it can be concluded that Mb:F (100:50) intercropping and use of AMF + B bio-fertilizer could be recommended to medicinal plant growers in sustainable production systems.