An investigation was conducted to study the effect of humic (HA) and fulvic acid (FA) on the dissolution of aluminum phosphate (AlPO4) and iron phosphate (FePO4), to analyze the dissolution products, and assess their availability to plants. The rate of dissolution was determined by shaking 10 mg of Al‐ or FePO4with 0 to 800 mg L‐1of HA or FA solutions at pH 7.0 for 0 to 192 hours. The phosphorus (P) concentration was measured in the extracts by spectrophotometry, whereas the nature of P‐humic acid complexes was determined by31P NMR analysis. Availability of dissolution products was studied by growing corn plants in aerated hydroponic solutions receiving treatments of 50 mg Al‐ or FePO4and 0 to 800 mg L‐1of HA or FA at pH 5.0. The results indicated that the amount of P released by HA or FA increased with time. Humic acid was more effective than FA in dissolving the metal phosphates. The31P NMR analysis showed that the dissolution products contained free orthophosphates and minor amounts of P‐humic acid complexes. This confirms the role of HA as a powerful chelator of Al and Fe, liberating in this way the orthophosphate anions. Corn plants grown in hydroponics, with AlPO4or FePO4as the source of P, exhibited better growth performance when HA or FA are present.