Interactions between Phosphorus and Humic Substances: Influence in P Bioavailability

A number of studies have reported the beneficial effects of the organic matter on the bioavailability of P in different soil types. These effects have been attributed to several factors, including the possible formation of phospho-metal-humic complexes, which could protect P from retrogradation in both acid and alkaline-calcareous soils. However, the experimental evidence supporting the existence of these complexes in solis is scarce and principally based on indirect arguments. The aim of this article is to describe the different studies carried out in our laboratory in order to characterize the formation and stability of these complexes, as well as their effect protecting P from soil retrogradation and their potential availability for plants. These results are discussed considered along with other present in the literature.