Compost Tea Quality and Fertility

Abstract

The water extract of compost termed “compost tea” retains all the beneficial soluble bioactive components, making it a potent source of plant stimulatory and defensive compounds. The exact nature and extent of these features are, however, modified by composting system, feedstock quality, tea preparation and resultant use and management, including application dynamics of the compost tea. Compost teas contain a significant quantity of total nutrients with the majority being primary macronutrients. Secondary and micronutrient concentrations are more variable, but contents are generally insufficient to satisfy crop requirements. Noting this, compost tea use in agriculture and horticulture supports crop nutrition directly and indirectly. Improvements in soil quality have been widely reported for a range of soils and compost teas. A key feature of compost tea-amended soils is the increase in soil organic matter and microbial diversity and its associated benefits. Research on appropriates rates for field and container use show large variability associated with edapho-climatic factors and crop species.However, foliar application seems best suited to maximising the dual nutrition and phytopathogenic effects of compost tea. Regardless of the purpose of compost tea use, its positive effects on crop growth and soil fertility, whilst controlling pest and disease, make it a contemporary sustainable tool aligned to organic agriculture.