Origins, roles and fate of organic acids in soils: A review

There is increasing evidence that the origins of organic acids (OAs) are as important as their roles and pathways of production. This review focuses on information about challenges associated with various aspects of OA production and release in the soil with the primary intention of harmonising different views to enable better understanding of this topic. A considerable body of work devoted to the understanding of origins, roles and dynamics of OAs in soil has been critically scrutinised for their various positions in this review. Organic acids in the soil originate from a variety of sources that may include plant roots, microorganisms and organic decomposition. Although OA synthesis in the soil environment may reflect a natural response of biological systems to biotic and abiotic stresses, they also play crucial roles in physiochemical processes such as mineralisation and solubilisation of poorly available and complex minerals as well as contribution to the carbon cycle and detoxification of metals. However, these roles are conceivably a pooled effect of soil OAs interacting with other factors (soil type, soil pH, microbes and other metabolites). The key challenge to elucidate and unravel the dynamics of OAs in the soil lies with the ability to explain and understand how OAs are released in the rhizosphere alongside other important metabolites, which perhaps influence the dynamics.