In recent decades, a greater knowledge of chitin chemistry, and the increased
availability of chitin-containing waste materials from the seafood industry, have led to the
testing and development of chitin-containing products for a wide variety of applications in
the agriculture industry. A number of modes of action have been proposed for how chitin
and its derivatives can improve crop yield. In addition to direct effects on plant nutrition
and plant growth stimulation, chitin-derived products have also been shown to be toxic to
plant pests and pathogens, induce plant defenses and stimulate the growth and activity of
beneficial microbes. A repeating theme of the published studies is that chitin-based
treatments augment and amplify the action of beneficial chitinolytic microbes. This article
reviews the evidence for claims that chitin-based products can improve crop yields and the
current understanding of the modes of action with a focus on plant-microbe interactions.