The excessive use of chemical fertilizers in conventional agricultural systems decreased the nutrient use efficiency and caused serious environmental problems such as waterway pollution, mineral depletion, soil acidification and other issues. In order to achieve the desirable essential oil productivity and reduction consumption of chemical inputs in peppermint (Mentha x piperita L.), a 2-year field experiment was carried out using a splitplot approach based on a randomized complete block design (RCBD), with 7 treatments and three replications at two harvesting times. The main factor was given by different fertilizer treatments including no fertilizer (control), chemical fertilizer, arbuscular mycorrhiza fungus, 50 % chemical fertilizer + arbuscular mycorrhiza fungus, nano chelated fertilizer, 50 % chemical fertilizer + nano chelated fertilizer, nano chelated fertilizer + arbuscular mycorrhiza fungus, and the sub-factor included two harvesting times (first harvest and second harvest). The results demonstrated that the highest and lowest growth parameters including plant height, number of lateral branches per plant and leaf greenness (SPAD index) were achieved with integrative application of 50 % chemical fertilizer + nano chelated fertilizer (in the first harvest) and control conditions (in the second harvest), respectively. Also, the maximum concentration of N, P, K and Fe was reached in the first harvest with application of 50 % chemical fertilizer + nano chelated fertilizer. Furthermore, the highest peppermint dry matter yield (354.8 g/m2 ), essential oil content (2.7 %) and essential oil yield (6.6 g/m2 ) was achieved at the first harvest with application of 50 % chemical fertilizer + nano chelated fertilizer. GC–MS analysis of peppermint essential oil showed that the major components at first harvest were menthol (31.82–۳۷٫۸۷ %), menthone (23.85–۳۰٫۹۰ %), ۱,۸-cineole (6.39–۶٫۸۲ %), δ-terpineol (3.61–۴٫۱۱ %) and neo-menthol (2.67–۳٫۳۳ %), whereas at second harvest menthol (44–۴۷٫۳۱ %), p-menth-L-en-9-ol (11.66–۱۴٫۹۶ %), menthofuran (3.44–۵٫۱۴ %), menthone (3.82–۱۰٫۶۲ %), ۱,۸-cineole (5.51–۵٫۹۹ %) and neo-menthol (5.03–۵٫۹۰ %). Notably, menthol reached the highest amount with application of 50 % chemical fertilizer + nano chelated fertilizer. Overall, an integrative application of chemical fertilizers with nano fertilizers can be suggested to farmers as an alternative and environmentally friendly strategy to improve the quali-quantitative characteristics of peppermint essential oil.
Nowadays, the rapid thrive of global population increased the requirements for food and energy, leading to the enhancement of agricultural productivity in regions with limited cultivation area (Liu and Lal, 2015; Chen and Yada, 2011). In the conventional agricultural systems, the excessive use of chemical inputs allowed to increase the agricultural productivity. Detrimental implications on the environment and human health from intensive agricultural practices and long-term use of chemical fertilizers have been well evidenced (Bansal, 2017). Intensive application of chemical fertilizers has di fferent negative impacts on environment including the aggregation of pesticides and fertilizers, soil erosion, soil and water pollution, genetic erosion, leaching of nutrients and reduction of agrobiodiversity (Daneshmandi and Seyyedi, 2019). The soil health management is crucial for ensuring ecological and agricultural productions and maintaining plant diversity. The negative impacts of chemical fertilizers forced the agrochemical companies to replace them with biofertilizers in sustainable agricultural systems in order to achieve a desirable crop productivity (Sharma et al., 2013). Over 80 % of plant species like those belonging to Fabaceae (Weisany et al., 2016), Asteraceae (Kapoor et al., 2007), Apiaceae (Kapoor et al., 2002) and Lamiaceae (Tarraf et al., 2017) establish mutualistic associations with arbuscular mycorrhiza (AM) fungi.