Evaluation of Quantitative and Qualitative Traits of the First and Second Cuttings of Peppermint (Mentha piperita L.) under the Influence of the Integrated Application of Conventional, Nano Fertilizers and Mycorrhizal

     In order to protect biodiversity, especially medicinal herb, and crude herbal drugs from the wild origin, Biological Diversity Act (2002) and Rule (2004) were enforced which compelled the herbal industries and medicinal plant growers for conventional cultivation of medicinal herbs. However, intensive cultivation of these medicinal herbs and herbal drugs to meet the global demand has led to aggravated use of chemical fertilizers and pesticides and consequently questioning their safety and integrity. Moreover, total fertilizer nutrient (N+P2O5+K2O) consumption was estimated at 170.7 and 175.7 million tons in 2010 and 2011, respectively which estimated consumption of N, P, and K fertilizers is expected to increase from current consumption levels by 172%, 175%, and 150%, respectively by 2050. Excessive using of chemical fertilizers caused serious environmental issues globally such as reduction of plant diversity, instability of economic yield, an increase of pest and disease damages, intensification of soil erosion. These increasing concerns regarding the negative impacts of these systems on the environment and human health suggest that more effort is needed to develop sustainable agricultural systems with higher productivity and improved efficiency. Application of nano-fertilizers and biofertilizers such as arbuscular mycorrhizal fungi (AM) is regarded as one of the promising approaches to increasing crop productivity. Nano-materials (NMs) are defined as materials that with at least one dimension less than 100 which can improve one or more nutrients absorption for plants and enhance their growth and yields. The AM fungi are a fundamental group of soil micro-organisms, symbiotically associated with nearly 80% of plant species.
Peppermint (Mentha piperita L.), which is a hybrid between Mentha spicata and Mentha Aquatica belonging to a family, Lamiaceae, is one of the most important essential oil-bearing plants. The objective of this experiment was an evaluation of the quantity and quality traits of peppermint under the integrated application of chemical and nano-fertilizers and arbuscular mycorrhizal fungi. In order to investigate the effects of different fertilizers on the quantity and quality of peppermint at the first and second cuttings, a field experiment study was carried out as split-plot in time based on a randomized complete block design (RCBD) with seven treatments and three replications and two cutting times at the faculty of Agriculture, University of Maragheh, Iran, in 2017. The main factor was different fertilizer treatments included no fertilizer (control), chemical fertilizer (CF), arbuscular mycorrhiza fungi (AMF) (Glomus mussels), 50% CF+ AMF, Nano-fertilizers (NF), 50% NF+ 50% CF, NF+ AMF and the sub-factor was cutting time (first and second cutting). In AM fungi treatments, 80 g of the soil containing mycorrhizal fungi hyphae and the remains of the root and spores (1000 g spore.10-1 g soil) was added to soil in planting times. Also, Nitrogen Nano-fertilizer used with 2 ml/L concentration. Moreover, phosphorus, potassium, iron and zinc Nano-fertilizers applied with 1 g.L-1 concentration. Furthermore, manganese Nano-fertilizer used in 0.5 g/L concentration. Additionally, the foliar application of Nano-fertilizers was carried out in two-stage (One month after the cultivation and one month after first cutting). The results demonstrated that the highest total dry matter yield (382.6 g.m-2) was achieved under 100% CF followed by 50% CF+ AMF and 50% NF+ 50% CF treatments, respectively. On the other hand, the highest (6.1 g.m-2) and lowest (2.9 g.m-2) essential oil yield were obtained under 50% CF+ AMF and control, respectively. Chemical analysis of the essential oil demonstrated that in all treatments, menthol, menthone, 1, 8 cineole, neo-iso menthol, neo-menthol, Menthofuran, and p-Menth-1-en-9-ol were the main dominant components. The highest amount of menthol was obtained in nano-fertilizer treatment and at the second cutting. Furthermore, monoterpene hydrocarbons were the major fraction of the essential oil in both harvests. Based on the results, integrative application of 50% CF+ AMF and 50% CF+ 50% NF had a higher significant impact on the morphological traits compared with other treatments. The highest dry matter yield was achieved in the second cutting with the application of CF that was not significantly impacted with 50% CF+ AMF and 50% CF+ 50% NF treatments. Also, the highest essential oil content was obtained the integrative application of 50% CF+ 50% NF that was 7.1% higher than CF in the first cutting. In addition, the essential oil yield productivity increased 198% with application of 50% CF+ AMF and 50% CF+ 50% NF compared with control. Based on the essential oil compounds, the highest (46.31%) and the lowest (26.73%) content of menthol was recorded in the second cutting fertilized with NF and first cutting fertilized with CF. Generally, based on the obtained results, integrative application of AMF and NF with 50% CF increased the quality and quantity productivity of peppermint compared with 100% CF.