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Spectral and Chemical Characterization of Phosphates Associated with Humic Substances

^a USDA-ARS, New England Plant, Soil, and Water Lab., Orono, ME 04469
^b Dep. of Plant, Soil, and Environmental Sciences, Univ. of Maine, Orono, ME 04469
^c Geol. & Environ. Sci. Dep., Stanford Univ., Stanford, CA 94305

View larger version (20K): [in a new window]   Fig. 1. Fluorescence characteristics of humic substances. Component 1 and 3 were contributed by fulvic acid-like organic matter materials, and component 2 humic acid-like organic matter materials. EFa, Elliott soil standard fulvic acid; EHa, Elliott soil standard humic acid; LHa, Leonardite standard humic acid; PHa, Pahokee peat reference humic acid; WFa, Waskish peat reference fulvic acid; WHa, Waskish peat reference humic acid.

View larger version (22K): [in a new window]   Fig. 2. FT-IR spectra of humic substances. NaP, trisodium phosphate dodecahydrate; WHa, Waskish peat reference humic acid; EHa, Elliott soil standard humic acid; WFa, Waskish peat reference fulvic acid; EFa, Elliott soil standard fulvic acid; PHa, Pahokee peat reference humic acid; LHa, Leonardite standard humic acid.

View larger version (34K): [in a new window]   Fig. 3. Solution 31P NMR spectra of humic substances. Spectra are plotted with 15 Hz line-broadening. WHa, Waskish peat reference humic acid; WFa, Waskish peat reference fulvic acid; EHa, Elliott soil standard humic acid; EFa, Elliott soil standard fulvic acid.

View larger version (20K): [in a new window]   Fig. 4. Soluble Pi in reaction mixtures in the absence and presence of Fe or Al ions (3.22 mM each). Each reaction mixture contains 0.322 mM P. Pi, KH2PO4; IP6, phytate; EHa, Elliott soil standard humic acid; EFa, Elliott soil standard fulvic acid; WHa, Waskish peat reference humic acid; WFa, Waskish peat reference fulvic acid. Values are averages ± standard deviations (n = 6).

View larger version (27K): [in a new window]   Fig. 5. Increase of soluble Pi by 3-phytase hydrolysis. Reaction mixtures contain 0.322 mM P and none (control) or 3.22 mM Fe or Al ions. Pi, KH2PO4; IP6, phytate; EHa, Elliott soil standard humic acid; EFa, Elliott soil standard fulvic acid; WHa, Waskish peat reference humic acid; WFa, Waskish peat reference fulvic acid. Values are averages ± standard deviations (n = 6).

View larger version (37K): [in a new window]   Fig. 6. Soluble Pi in reaction mixtures in the absence and presence of 3-phytase in low- and high-molecular weight fractions of Elliott soil humic substances. EHa, Elliott soil standard humic acid; EFa, Elliott soil standard fulvic acid. Values are averages ± standard deviations (n = 3).

View larger version (32K): [in a new window]   Fig. 7. Soluble Pi in reaction mixtures in the absence and presence of 3-phytase soil. Before the enzymatic incubation, the humic substance solutions were irradiated by UV light for 4 h. EHa, Elliott soil standard humic acid; EFa, Elliott soil standard fulvic acid. Values are averages ± standard deviations (n = 4).