Soil controls on carboxylate-driven processes and opportunities

Abstract

Through their influence on microbial processes, carboxylates exuded by roots are key drivers of nutrient acquisition and organic carbon (C) storage in terrestrial ecosystems. However, the simultaneous interactions between environmental factors controlling the production and fates of carboxylates lead to uncertainty in understanding their role in terrestrial ecosystems. Here we suggest a more integrative view which points out that carboxylate-driven processes (metal chelation and formation of organo-mineral associations) can vary according to the soil physicochemical context. We show that variation in soil properties can substantially influence plant production of C surplus and discharge as root exudates. In addition, the control of soil processes (adsorption, complexation, leaching and biodegradation) on carboxylate fates is strongly governed by the physicochemical context. To illustrate this, the first soil scenario we present is characterized by fine-textured and nutrient-rich soils, which leads to a relatively lower root exudation rate but high potential of carboxylate associations with minerals. This soil context is more inclined to contribute to soil C storage. In the second scenario, coarse-textured and nutrient-poor soils lead to higher rates of carboxylate production and higher carboxylate ability to mobilize nutrients through chelation. In this case, the carboxylate-induced mobilization of nutrients is maximized. We wish to emphasize the need to integrate the diversity of soil properties when it comes to propose regenerative agricultural practices that capitalize on the carboxylate-driven soil processes and their related ecological functions, whose potential benefits must be evaluated on a case-by-case basis according to the soil physicochemical context.