Chemical compositions of essential oil and antioxidant activity of dragonhead (Dracocephalum moldavica) in sole crop and dragonhead- soybean (Glycine max) intercropping system under organic manure and chemical fertilizers

Organic manure can be used as an alternative for chemical fertilizers in sustainable agriculture. In addition, compared with sole cropping systems, intercropping is a promising approach for the crop production due to its lower reliance to chemical fertilizers. In this study, grain yield of soybean and biomass, chemical compositions and antioxidant activity of dragonhead essential oil in sole crop and dragonhead-soybean intercropping system under organic and chemical fertilizers were investigated. Land equivalent ratio (LER) was calculated as well. Results indicated intercropping and application of organic manure, increased soybean grain yield and dragonhead biomass. The LER value for soybean: dragonhead with ratios of 1:1 and1:2 under organic manure was greater than 1, indicating superiority of intercropping versus sol crop systems. GC-MS analysis showed that geranial, geranyl acetate, neral and piperitone were major compounds of dragonhead. The geranial and neral contents were increased in sole cropped dragonhead with application of chemical fertilizer, while the piperitone content was enhanced in sole cropped plants fertilized with organic manure. The highest of geranyl acetate content was observed in intercropped dragonhead plants fertilized with chemical fertilizer. Addition of organic manure lead to increase the antioxidant capacity of dragonhead in intercropped plots. The highest antioxidant activity of dragonhead (IC50 = 1.45 μgmL−1) was observed in one row of soybean + two rows of dragohead treated with organic manure. Overall, one row of soybean + two rows of dragohead with use of organic manure was more productive and had the highest LER value, antioxidant activity and a large amount of chemical compositions of essential oil. Thus this treatment could be adopted by the medicinal plant growers for appropriate production of dragonhead.