عنوان مقاله [English]
Introduction Lamiaceae, formerly called Labiatae, the mint family of flowering plants with 236 genera and more than 7,000 species, the largest family of the order Lamiales and many species are cultivated for their fragrant leaves and attractive flowers. Thymus daenensis is native to Iran and growing in many parts of Iran, the plant is extensively used in folk medicine and has a wide variety of essential oils. Medicinal and aromatic plants have antioxidant compounds such as polyphenols which decrease oxidative stress in cells of plants and animals. In recent decades, excessive use of chemical fertilizers in order to increase the yield of agricultural products has caused many problems in economic and environmental aspects.
The biofertilizer plays an important role in nitrogen fixation, iron sequestration, and phosphate solubilization, thus making these complex organic molecules available for utilization by the plants.
Biofertilizers are the microbial inoculants that colonize the rhizosphere and improve plant growth by enhancing nutrient accessibility to plants. However, biofertilizers perform more than one mechanism for accomplishing plant growth enhancement. These abilities are of great agriculture importance as far as crop yield and soil fertility improvement is concerned, thus decreasing the ill effects of chemical-based fertilizers in our environment. For instance, excessive use of chemical N fertilizers causes soil acidifcation and, thus, groundwater and atmospheric pollution. Nonetheless, synthesis of chemical fertilizers is highly energy-consuming processes. Chemical based fertilizers impose long-lasting effects on the atmosphere in terms of carbon footprint, eutrophication, and soil fertility decline. However, the control of chemical and biological properties of soil is important in the quantity and quality of agricultural crops. Few reports reveal that in case of controlled soil conditions, signifcant enhancement in crop production was achieved through biofertilizer applications. Thus, this research was carried out with the aim of studying the effect of independent and combined use of biological and chemical fertilizers on quantitative and qualitative properties of thyme.
Materials and Methods The aim of this study was to investigate the effect of biofertilizers (phosphate Barvar-2 and Azotobacter), manure (cow manure), and chemical (NPK) on quantitative and qualitative characteristics of Thymus daenensis. Physicochemical properties of study soil (calcium carbonate equilibrium, pH, OC, EC, micro and macro elements, soil texture) and was determined by standard methods. A factorial experiment based on randomized completely design was carried out with eight treatments including chemical fertilizer (100%), biofertilizers (phosphate Barow-2 and Azotobacter) (100%), cow manure (100%), combined treatment: chemical + biofertilizer 50%, chemical + cow manure 50%, biofertilizer,+ cow manure 50%, biofertilizer + chemical + cow manure 50% and control at three replications. Seeds of Thymus daenensis were treated before cultivate with biofertilizers (phosphate Barvar-2 and Azotobacter) with 100 g ha-1 based on the recommended guidelines (10^8 active bacteria g-1 of biofertilizer). Seeds were cultured in perlite and pit moss culture beds. Transplant was transmitted to the farm at the end of April. Thymus product was harvested at flowering stage. Economic performance of thymus including leaf and inflorescence weight was calculated after drying of bushes. Essential oil content was measured using clevenger. Physiological and antioxidant propertiese including chlorophyll a and b, total chlorophyll, cartenoids, total phenolic content and flavnoieds were measured (Lichtenthaler and Wellburn, 1987; Horwist, 1984). Essential oil yield was obtained from essential oil percentage in dry matter yield of thymus.
Results The results showed that the integrated application of biofertiliizers was significant in qualitative and quantitative characteristics of Thymus daenensis. Based on the results, shoot dry yield (156.26 g m-2), essential oil yield (5.36 g m-2) and economic yield (74.72 g m-2) in 50% chemical fertilizer + biofertilizer + cow manure treatment were higher as compared to other treatments. Integrated application of organic and chemical fertilizers improved the content of photosynthetic pigmentation and increased the concentration of iron (Fe), zinc (Zn) and copper (Cu) in thymus. Aso, combined application of 50% chemical fertilizer + biofertilizer + manure increased total phenol (30.12%), flavonoids (22.26%) and antioxidant activity (15.95%) of thymus compared to control treatment.
Conclusion The results showed that the chemical fertilizers to start production and compensate for the fertilizer source and biofertilizers for the continuous of the presence of nutrients in soil are important. Consequently, the combination of chemical fertilizer (NPK) and biofertilizers could be recommended as a suitable nutrition source for plant as well as the improvement of soil physical and chemical properties. Accordingly, chemical fertilizers consumption are hazardous for human severely affect ecological balance in the environment. Therefore, the success related to biofertilizers depends on inventions of innovative strategies which are related to the functions of different beneficial bacteria and their proper application to the fields through advanced and improved techniques.