Intercropping, the practice of growing two or more crops in proximity, is recognized as a vital component of sustainable agriculture. A recent study by Zahra Amiriyan Chelan, Amini, and Adel (2023) investigated the effects of chemical fertilizer (CF), arbuscular mycorrhizal fungi (AMF) from the Glomus species, and a combination of AMF with nitrogen-fixing bacteria (NFB), specifically Azospirillum and Azotobacter, on the yield and composition of essential oil from Moldavian balm (Mb) (Dracocephalum Moldavia L.). The study analyzed these treatments in sole cropping and intercropping with fenugreek (F) (Trigonella foenum-graecum L.).
The experiment in East Azarbayjan, Iran, spanned two growing seasons in 2020 and 2021. It yielded impressive results. The highest dry herbage yield, measuring 6132 kg per hectare, was found in an intercropping combination of four parts Moldavian balm and two parts fenugreek using chemical fertilizer. In terms of essential oil yield, an intercropping ratio of Moldavian balm to fenugreek (4:2) under AMF and NFB treatment produced the highest output at 15.28 kg per hectare, only second to the yield from the sole-cropped Moldavian balm.
The essential oil was rich in various beneficial chemical constituents, including geranial, geranyl acetate, geraniol, neral, and nerol. The combined use of AMF and NFB was found to significantly increase the geranial content in the essential oil in various intercropping patterns, showing an increase of 25.1%, 15.5%, and 34.6% for Mb: F ratios of 1:1, 2:2, and 100:50 respectively when compared to the sole cropping of Moldavian balm.
Moreover, the study revealed the highest Land Equivalent Ratio (LER) values, which measure the relative efficiency of intercropping versus sole cropping, in the 100:50 Moldavian balm to fenugreek intercropping pattern in 2021. The LER values were 1.70 and 1.63 for chemical fertilizer and AMF plus NFB treatments, respectively.
In conclusion, the study demonstrates that intercropping and bio-fertilizers can contribute to sustainable agricultural practices and improve the yield of essential oils in medicinal plants. The researchers particularly recommend the combination of Moldavian balm and fenugreek in a 100:50 ratio and using AMF combined with NFB bio-fertilizer for growers aiming at sustainable production systems.
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