Document Type : Research Paper

Authors

• A. Javanmard ¹
• Mosa Jamali ²
• M. Morshedloo ³
• M. Nouraein ⁴
• M. Amani machiani ⁵

¹ Department of production and genetics, faculty of agriculture, university of maragheh

² Ph.D student of Agrotechnology-Crop Ecology, Department of Plant Production and Genetics, Faculty of Agriculture, University of Maragheh, Maragheh, Iran

³ Assoc. Prof., Department of Horticultural Science, Faculty of Agriculture, University of Maragheh, Maragheh, Iran.

⁴ Academic member, Dept. of Plant Production and Genetics, Faculty of Agriculture, University of Maragheh,

⁵ Department of Plant Production and Genetics, Faculty of Agriculture, University of Maragheh, Iran.

Abstract

Background and objectives: In recent years, green manure has received attention due to its positive effects on soil health and the quality and quantity of plants. It has been reported that intercropping legumes with cereal as green manures improves soil fertility and nutrient availability, increasing plant productivity. In addition to green manures, applying organic (vermicompost) and biofertilizers (arbuscular mycorrhizal fungi) can positively affect the plant's productivity and quality. Considering the adverse effects of chemical fertilizers on the bio-active compounds of medicinal and aromatic plants, improving the quantity and quality characteristics, especially in low-input conditions, has become a significant challenge in the agricultural sector. Therefore, the study aimed to investigate the effectiveness of green manures and bio- and organic fertilizers on the nutrient content and morphological and phytochemical characteristics of peppermint.
Methodology: The experiment was conducted as a randomized complete block design (RCBD) with 8 treatments and three replications at the Faculty of Agriculture, University of Maragheh, Iran, in 2022. The treatments included green manures [barley monoculture, hairy vetch monoculture and replacement intercropping of 75% hairy vetch+ 25% barley, 50% hairy vetch+ 50% barley and 25% hairy vetch+ 75% barley], arbuscular mycorrhizal fungi (AMF) and vermicompost. Before harvesting, peppermint's growth characteristics, including plant height, number of leaves, number of nodes, and number of lateral branches, were randomly measured in 10 samples from each treatment. To measure the dry matter yield of peppermint, 3.2 m2 of each plot was harvested randomly after removing the marginal effects. The peppermint EO was extracted using a Clevenger by water distillation. Moreover, the EO constituents were analyzed using GC-MS (GC–MS; 5977A, Agilent) and GC-FID (Agilent 7990B). Data analysis was performed with SAS (version 9.3) software. Also, the significant differences among means were compared with the LSD test at P< 0.05.
Results: The results demonstrated that the highest N (18.05 g kg-1) and K (18.25 g kg-1) content was obtained by applying green manure as intercropping of 50% hairy vetch+50% barley. However, the highest content of P (1.75 g kg-1) was achieved in the AMF application. The maximum dry yield of peppermint (292.67 g m-2) was observed when green manure was applied as an intercropping of 50% hairy vetch+50% barley, which had no significant difference from the AMF application. Additionally, the maximum essential oil content (1.84%) and essential oil yield (5.39 g m-2) was achieved by applying green manure as intercropping of 50% hairy vetch+50% barley. The essential oil analysis showed that the significant constituents of peppermint essential oil were menthol (32.74-38.06%), menthone (18.33-21.42%), and 1,8cineol (5.20-6.12%). The maximum content of menthol and cineol was obtained by applying green manure as intercropping of 50% hairy vetch+50% barley.
Conclusion: Generally, the study results demonstrated that applying green manure as intercropping of 50% hairy vetch+50% barley as a sustainable strategy can improve peppermint's essential oil quantity and quality.

Keywords

• Mycorrhiza fungus
• sustainable agriculture
• essential oil quality
• menthole
• cineol

Main Subjects

• Improvement and breeding