Efficacy of organic amendments used in containerized plant production: Part 1-Compost-based amendments

Organic amendments added to growing media are claimed to improve plant growth by mechanisms such as providing nutrients, stimulating growth, enhancing flowering and fruiting, increasing beneficial microbes and controlling diseases and pests. However, the claims have received relatively little scientific scrutiny, particularly in containerized plant production. The aim of this review was to evaluate the efficacy of compost-based organic amendments in containerized production horticulture, including composts and vermicomposts produced from plant residues, animal manures, and municipal and industrial wastes; compost teas; and vermicompost teas. Their features and drawbacks, suitability and typical application rates in specific production systems, and knowledge gaps are identified. The variability within and among compost-based organic amendments makes it difficult to generalize about their utility to containerized plant production, however grape marc compost and green waste compost have the widest application in vegetable and ornamental species, respectively.