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Characterization of Phosphorus in a Spruce‐Fir Spodosol by Phosphorus‐31 Nuclear Magnetic Resonance Spectroscopy
Author(s) -
Dai K'o H.,
David Mark B.,
Vance George F.,
Krzyszowska Anna J.
Publication year - 1996
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1996.03615995006000060046x
Subject(s) - forest floor , chemistry , podzol , pyrophosphate , soil horizon , soil water , horizon , phosphorus , environmental chemistry , biogeochemical cycle , mineralogy , organic matter , geology , soil science , mathematics , organic chemistry , geometry , enzyme
Factors affecting the distribution and biogeochemical cycling of soil P are only partially understood. Many previous studies have focused on P distribution within surface mineral soils and cycling of inorganic P. Few data are available on organic forms of P in forest floor and mineral horizons of forest soils. Therefore, we used 31 P nuclear magnetic resonance ( 31 P‐NMR) to characterize the P compounds in NaOH‐ethylenediaminetetraacetic acid (EDTA) extracts of three Spodosol profiles. The NaOH‐EDTA extracted most of the P in the three organic horizons (87, 83, and 69% of total P in Oi, Oe, and Oa horizons, respectively) and 39 to 67% in the Bhs horizon. Major P species detected in all horizons were inorganic orthophosphate and orthophosphate monoesters and diesters that ranged from 11 to 53%, 12 to 52%, and 13 to 45% of total P extracted, respectively. As is typical in Spodosol chemistry, considerable variation was found for organic P distribution in the organic horizons of the three profiles. However, on average, distribution patterns of P forms with depth were observed, including a decrease in the proportion of inorganic orthophosphate with greater decomposition in the forest floor (Oi > Oe > Oa), followed by an increase in the Bhs horizons. Pyrophosphate (5–19% of total P) and polyphosphates (5–13% of total P) were found mainly in the forest floor horizons, except for one profile where pyrophosphate had evidently accumulated in the Bhs horizon. Traces (≈2%) of phosphonates occurred only in the Oa horizon. Results suggest that biological activity, extractable Fe concentration, structural characteristics of P compounds, and pH are probably responsible for the distribution of P species in these Spodosols.