بررسي تأثير كودهاي آلي و شيميايي بر عملكرد برگ، درصد و اجزاي اسانس به ليمو (Lippia citriodora Kunth)

Effects of Organic and Chemical Fertilizers on Leaf Yield, Essential Oil Content and Composition of Lemon Verbena (Lippia citriodora Kunth)

با توجه به افزایش تقاضا در بازار در حال رشد فرآورده‌های دارویی با منشا گیاهی، تولید ارگانیك و ارتقاء كیفیت ماده‌ی خام اولیه بایستی اولین هدف جهت توسعه‌ی این محصولات باشد. در این راستا آزمایشی گلدانی بر پایه طرح كاملاً تصادفی با شش تیمار و سه تكرار بر روی گیاه دارویی به لیمو در سال ۱۳91 و در گلخانه تحقیقاتی گروه علوم باغبانی دانشكده كشاورزی دانشگاه تربیت مدرس صورت پذیرفت. تیمارها شامل استفاده از ورمی‌كمپوست به میزان 10، 20 و 30 درصد حجم گلدان، ورمی‌واش، كودكامل و شاهد (بدون كود) بودند. پس از برداشت برگ‌ها در مرحله شروع گلدهی، اسانس آن‌ها استخراج شد و سپس به‌وسیله دستگاه GC و GC/MS مورد تجزیه قرار گرفت. نتایج نشان داد كه بیشترین عملكرد برگ (73/7 گرم) و میزان اسانس (1/1 درصد) مربوط به تیمار استفاده از 30 درصد ورمی‌كمپوست در گلدان بود و كمترین عملكرد برگ (75/4 گرم) و محتوای اسانس (8/0 درصد) به تیمار شاهد تعلق داشت. در بررسی اجزای اسانس، بیشترین میزان سیترال (9/54 درصد) متعلق به تیمار كود كامل بود ولی بیشترین میزان لیمونن و 8/1 سینئول (به ترتیب 4/7 و 8/8 درصد) در تیمار استفاده از 30 درصد ورمی‌كمپوست در گلدان مشاهده شد. همچنین در بررسی گروه‌های اجزای اسانس، تیمار 30 درصد ورمی‌كمپوست بیشترین مقادیر مونوترپن های هیدروكربنی و اكسیژن‌دار (به ترتیب 4/12 و 3/63 درصد) را به خود اختصاص داد. با توجه به نتایج این تحقیق به نظر می‌رسد كه كود ورمی كمپوست می‌تواند به عنوان جایگزین مطلوب كودهای شیمیایی در راستای تولید ارگانیك به لیمو با كمیت و كیفیت مواد موثره بالا استفاده شود.

Introduction: Organic fertilizers with beneficial effects on soil structure and nutrient availability help maintain yield and quality, and they are less costly than synthetic fertilizers. Vermicompost and vermiwash are two organic fertilizers that they contain a biologically active mixture of bacteria, enzymes and phytohormones, also these organic fertilizers can supply the nutritional needs of plants. Lemon verbena (Lippia citriodora Kunth, Verbenaceae) is an evergreen perennial aromatic plant. The lemon-scented essential oil from the lemon verbena has been widely used for its digestive, relaxing, antimalarial and lemony flavor properties. In order to decrease the use of chemical fertilizers for reduction of environmental pollution, this research was undertaken to determine effects of vermicompost and vermiwash in comparison with chemical fertilizer on leaf yield, essential oil content and composition of lemon verbena. Materials and Methods: A pot experiment based on a completely randomized design with six treatments and three replications on Lemon verbena was carried out in the experimental greenhouse of the Department of Horticulture Sciences, Tarbiat Modares University, 2012. Treatments consisted of 10, 20 and 30 % by volume of vermicompost and vermiwash (with an addition to irrigation in three steps, including: two weeks after the establishment of plants in pots, the appearing of branches and three weeks before harvest), complete fertilizer and control without any fertilizer. Each replication contained six pots and each pot contained one plant of Lemon verbena provided from Institute of Medicinal Plants, Karaj, therefore 108 pots were used in this experiment. The pots were filled up by a mixture contained 3/5 soil and 2/5 sand (v/v). After three months, plant aerial parts were harvested concomitantly at starting of the flowering stage. Aerial parts were dried at room temperature for 72 hours and dry weights of dried branches and leaves were measured. For isolation of essential oils, about 20 g of dried leaves (three replications of each treatment) was subjected to hydro-distillation for 2 h with a Clevenger apparatus. The extracted essential oils were dried over anhydrous sodium sulphate and then they analyzed by GC and GC/MS. The data were subjected to analysis of variance using SAS software and means compared with Duncan 's multiple range test. Results and Discussion: The results showed that differences between treated plants with organic fertilizers were not significant for aerial part yield, but leaf yield and essential oil content were affected by fertilizer type (p <0.05). The maximum amount of leaf yield (7.73 g) and essential oil (1.1 %) was in using of 30 % vermicompost in the pots and the lowest (4.75 g and 0.8 %) belonged to the control treatment. Twenty-two compounds were identified in the essential oils and neral, geranial, limonene, 1, 8-cineole were the most important compounds of the essential oils. The highest amount of citral (54.9 %) obtained from the complete fertilizer treatment but the maximum amount of limonene and 1,8- cineol (respectively 7.4 and 8.8 %) determined in the treatment of using 30 % vermicompost in the pot. In survey of the groups of essential oil components, the maximum amount of monoterpene hydrocarbons and oxygenated monoterpenes (respectively 12.4 and 63.3 %) belonged to using 30 % vermicompost in the pot. It would be suggested that Vermicompost by improving the bacterial activity, water holding capacity and physical properties of the soil promotes growth of plants. Also vermicompost and vermiwash contain cytokinins, auxin, amino acid, vitamins and enzymes that they can promote growth factors and aerial parts yield. Essential oils are terpenoid compounds that they need NADPH and ATP for their biosynthesis in medicinal and aromatic plants and N and P are major elements for them. Vermicompost can increase the essential oils in plants with providing more N and P elements. Conclusion: The application of organic fertilizers may help alleviate soil erosion and saline and sodium problems as a result of excessive chemical fertilization. The results showed that vermicompost compared to vermiwash and chemical fertilizer had greater impact on yield and essential oil content of lemon verbena. Vermicompost also has a positive impact on the major components of the essential oil and the highest level of monoterpene hydrocarbons and oxygenated monoterpenes belonged to this treatment. According to the results, it seems that the application of vermicompost is an ideal alternative for chemical fertilizers in organic farming of Lemon verbena with high quantity and quality of active substances.