Composting is a biological process where biodegradable organic compounds are transformed into compost. In the last years, in agriculture, the use of new products derived from compost, such as compost-tea (CT) is increasing, due to their positive effects on the crops. In particular, they show positive effects both on biological control of diseases and on stimulating plant growth, with subsequent interesting improvement of quantity and quality of crop productions. CT is produced from compost by extraction and/or fermentation processes, conducted in liquid phase, for a period of time from few hours to two weeks, with or without active aeration and with or without the addition of nutrients (molasses, casein, etc.). These factors influence the effectiveness of the product, in particular the quality of its biotic and abiotic component. Indeed, the presence in the CT of soluble organic molecules, such as humic substances, and useful microorganisms, such as bacteria, fungi, protozoa and nematodes, have positive effects on suppression of diseases and on plant growth promotion. As result of a growing need of a sustainable agriculture and food security, the use of CT is increased. These formulates have shown important suppressive capability and can improve the efficiency of absorption of mineral nutrients, influencing plant physiology. The goal of this work is to illustrate principal results about the use of CT in plant protection and growth promotion in horticulture.
Keywords: disease suppressiveness, liquid state fermentation, organic matter, plant nutrition, sustainable agriculture