The functional role of organic acid anions in soil has been intensively investigated, with special focus on(i) microbial respiration and soil carbon dynamics, (ii)nutrient solubilization or (iii) metal detoxification andreduction of plant metal uptake. Little is known about the interaction dynamics of organic acid anions with thesoil matrix and the potential impact of adsorption and desorption processes on the functional significance ofthese effects. The aim of this study was to characterize experimentally the adsorption and desorption dynamicsof organic acid anions in five agricultural soils differing in iron and aluminium oxide contents and using citrateas a model carboxylate. Results showed that both adsorption and desorption processes were fast in all soils,reaching a steady state within approximately 1 hour. However, for a given total soil citrate concentration(ct)the steady state was critically dependent on the starting conditions of the experiment, whether most ofthe citrate was initially present in solution (cl) or held on the solid phase (cs). Specifically, desorption-ledprocesses resulted in significantly smaller steady-state solution concentrations than adsorption-led processes,indicating that hysteresis occurred. As it is not possible to distinguish between different adsorption anddesorption pools in soil experimentally, a new dynamic hysteresis model that relies only on measured soilsolution concentrations was developed. The model satisfactorily explained experimental data and was able topredict dynamic adsorption and desorption behaviour. To demonstrate its use, we applied the model to tworelevant situations involving exudation and microbial degradation. The study highlighted the complex nature ofcitrate adsorption and desorption dynamics in soil. We conclude that existing models need to incorporate bothtemporal and hysteresis components to describe realistically the role and fateof organic acids in soil processes.