Resumen:
The aim of this review is to describe the main physicochemical characteristics of diverse typesof humic-metal-phosphate acid complexes. The effects of these complexes on phosphorus (P)fixation in soils with different pH values and physicochemical features and on plant phosphorusuptake are also discussed. Humic-metal-phosphate complexes have apparent stability con-stants in the same range as those of metal-humic complexes, in solutions with diverse pH andionic-strength values. Likewise, the molecular-size distribution of humic-metal-phosphate com-plexes as a function of pH is similar to that of potassium or sodium humates and metal-humiccomplexes. Humic-metal-phosphate complexes are able to decrease phosphate fixation in soilsand increase plant growth and phosphate uptake. Phosphorus fertilizers containing humic-metal-phosphate complexes proved to be efficient to improve plant growth and P uptake withrespect to conventional fertilizers such as single superphosphate. The values of parametersrelated to plant phosphorus-utilization efficiency (PUt E) suggest that the regulation of rootacquisition of phosphate from these complexes could involve the interregulation of a system forthe optimization of metabolic P utilization in the shoot and another system involving stressresponses of roots under phosphorus deficiency.
