ROLE OF EDDHA AND HUMIC ACIDS ON THE SOLUBILITY OF SOIL-PHOSPHORUS

A greenhouse pot experiment was designed in order to test the effect t hat the addition of two organic materials, EDDHA and humic acid would have on the availability of P released from three P fertilizers, 8-24- 8, 20-20-20, and MAP (monoamonium phosphate). Phosphorus was extracted from soil by three different methods (Burriel-Hernando, Olsen, and EU F). Burriel-P and EUF-P were correlated according to the equation: Bur riel-P = 3.9 x Fraction I + 2. 7 x Fraction II + 23.5: r = 0.7558 wher e: Fraction I = EUF-P, 200 V, 30 min; and Fraction II = EUF-P, 200 V, 5 min. This relationship indicates that the Burriel-Hernando method ex tracts both, soluble and insoluble forms of P. The effect of the organ ic additions depend basically on the kind of fertilizer employed. EDDH A increased P availability from 8-24-8, and humic acid did the same fo r MAP. The differences between treatments for 20-20-20 were also depen dent on the method of P extraction.