## 1 Introduction  
The need for a reduction in the environmental impacts of synthetic pesticides and the new trends dictated by the market for organically managed cropping systems, has renewed interest in agricultural practices of the past, based on natural products, such as compost teas (CTs), which have been found to be effective in the control of many plant diseases [1]. CT is defined as an organic liquid formulate, obtained by water extraction of a quality compost, continuative for a defined period, under aerated (aerated CT, ACT) or not aerated (non-aerated CT, NCT) conditions, with or without nutritional additives [2]. CT has been proposed to be applied to soil and/or to plants through irrigation systems, soil drenching, or foliar spray with different aims, including control of leaf and/or soil crop diseases; microbial augmentation for restoring or increasing beneficial telluric microflora able to promote soil health; stimulation of the general plant physiological performances; and nutrients supply [3, 4, 5, 6, 7, 8, 9].  
This agro-technique has been used under organic and biodynamic farming since 1920 [10]. It is stated that CTs exert positive actions due to the presence of soluble organic molecules, such as humic substances (humic and fulvic acids). These molecules may have a direct effect on plant metabolic processes (i.e., radical bio-stimulation, photosynthesis,respiration, activation of enzymes, mineral nutrition) due to their hormone-like molecular structures [11; 12; 13]. In addition, the great amount and diversity of beneficial Prokarya and Eukarya microorganisms contained in bioactive CTs generally play a crucial role in crop protection, as well as in biostimulation and/or biofertilization [3; 4; 14; 15; 16]. Nutritional additives, such as rock dust, humic and fulvic acids, molasses, yeast extracts, fish and dairy byproducts, green algae and plant extracts, glucose, sucrose, starch, chitin, cellulose, wheat straw, etc., can be added into the extracting volume with the aim of significantly affecting the major microbial CT component by enriching population levels and conditioning their compositions and structures. In addition, the promotion of microorganism survival, as well as the improvement of plant pathogen suppression properties, occur when the additives are distributed on soil and/or plant surfaces [17; 18]. Doubts have arisen on the use of CTs with nutritional additives for the treatment of crops to be destined for fresh markets. Several Authors [17; 19; 20; 21] have highlighted the risks of this practice in favoring the regrowth of human pathogenic bacteria, such as _Salmonella_ and _Escherichia coli_, causing problems for public health. On the other hand, this circumstance can be totally avoided by controlling the starting compost quality and the overall hygienic conditions occurring during the tea preparation process.  
Available literature surveys revealed the necessity to further examine the effects of source materials (e.g., compost from livestock matrices), extracting media, and environmental conditions during the extraction process, on the quality of CT and, then, on its functionality [19; 21].  
This study is designed to assess the hypothesis that the use of additives will modulate CT quality, influencing their agronomical and crop defence properties. Thus, the present research aims to characterize the chemical-physical and microbiological quality of a set of aerated CTs, obtained through water-mediated extraction of a green/municipal waste compost, with two different additives, whey and molasses, at increasing concentrations. In detail, the content of mineral elements and total heavy metals, pH and EC during the extraction process, the main microbial population, the functional biodiversity and pathogen suppression capacity, were assessed. This information can be useful to fill the gaps in the literature and provide scientific value to a practice that usually shows an empirical and extemporaneous character.