Effects of Microelements and Plant Density on Biomass and Essential Oil Production of Peppermint (Mentha piperita L.)

摘要

Peppermint (Mentha piperita L.) is one of the highly demanded aromatic medicinal plants and its essential oil is extensively used in the food, flavor and pharmaceutical industries. A field experiment was carried out during 2005-2006 at the Research Farm of the University of Tabriz. In this research, the effects of four plant densities (8, 12, 16 and 20 plants m 2) and two microelement treatments (non spraying or spraying a mixture of 20 kg ha 1 HBO3, 25 kg ha 1 ZnSO4 and 15 kg ha 1Fe) on biomass and essential oil production of peppermint were evaluated at two cuttings. These treatments were arranged in a factorial experiment on he bases of randomized complete block design with three replications. The results of first cutting showed that the foliar application of microelements increased fresh and dry matter and leaf area of plants. Also, in the first cutting, bush and leaf essential oil percentage and essential oil yield increased with spraying of micronutrients. Dry matter and essential oil production of first cutting plants increased by increasing plant density. In the second cutting, the foliar application of microelements had only significant effects on leaf essential oil percentage and essential oil yield of peppermint. The result of two cuttings indicated that peppermint performed better in first than in second cutting. Plants harvested in first cutting had higher height, fresh and dry matter and essential oil yield (20.02 li ha 1), but they had lower bush and leaf essential oil content. Therefore, the highest leaf essential oil percentage (2.96%) obtained with spraying of microelements in the second cutting.