## 1 Introduction  
Management strategies in conventional farming systems are strongly characterized by an increased use of fertilizers and pesticides, an excessive use of water irrigation and, in general, an establishment of intensive crop cultivation systems. This context led cropping systems to be less resilient to changing environmental conditions, negatively affected soil quality as well as resulted in serious risks to human health and the environment. In recent years, efforts have been directed toward sustainable farming systems to reduce inputs of chemical fertilizers, pesticides, and water and achieve the goal of an economically viable and environmentally friendly agricultural production system. Among sustainable techniques, the use of biostimulants and/or biofertilizers is considered a new and environmentally friendly agricultural practice that satisfies both crop intensification and environmental protection. A plant biostimulant is any substance or microorganism applied to plants that enhances nutrition efficiency, biotic and abiotic stress tolerance, and/orcrop quality. The use of biostimulants may also increase plant productivity. By extension, with the name \"plant biostimulants\" could be also designated commercial products containing mixtures of such substances and/or microorganisms [1] and this definition can also include the synthetic microbial consortium also called Effective Microorganisms (EM) and Olive Mill Wastewater (OMW). Generally, EM consists mainly of photosynthetic bacteria, lactic acid bacteria, yeast [2] and it is a registered trademark and a brand name owned by EM Research Organization (EMRO). This microbial consortium could increase organic matter and provide nutrients, thus being an alternative sustainable practice in sustaining plant production without other external inputs such as chemical fertilizers and pesticides and without increasing excessive costs [3; 4]. On the other hand, OMW could represent a strategic resource in integrated agricultural system management, since it would meet the two-fold objectives of eliminating olive oil waste and using it beneficially to improve soil fertility [5; 6]). The characteristics of OMW are variable and depend on the geographic site, plant cultivar and maturity, climatic conditions, cultivation/processing procedures, and oil extraction processes [7; 8]. Commonly OMW has high chemical and biological oxygen demand as well as high amounts of total phenols, carbohydrates, polysaccharides, fatty acids, polyalcohols, pectins, and tannins [9; 10] that represent a lignin-like structure and constitute the most resistant fraction of this waste stream [11]. OMW usually has a high level of toxicity for the presence of various phenolic compounds, but with appropriate measures and dilutions can be used in agriculture for plants cultivation [12]. The high-polluting power of OMW is related to the presence, in this wastewater, of a high concentration of organic compounds and phenolic acids which confer dark color and low pH. These characteristics make OMW toxic if disposed into the soil, because it can alter the microbial soil composition and its structure, with strong impact to the environment. In this study the effect of the application of EM and OMW on _Tanucetum balsamita_ L. was assessed. _Tanucetum balsamita_ L. (_Chrysantenum balsamita_ L., _Balsamita major_ Dest., _Balsamita vulgaris_ Willd. ; Asteraceae family) is a medicinal perennial plant species native of Southern Europe and Western Asia, and it is also known as cotrans. Its first botanical description was carried out in the 9 th Century by months who classified all the official plants in their gardens [13]. Due to its strong mini-like aroma and bitter taste, it is used to aromatize foods, cakes, drinks and to prepare potpourri [14].