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A 31 P nuclear magnetic resonance study of the phosphorus species in alkali extracts of soils from long‐term field experiments
Author(s) -
HAWKES G. E.,
POWLSON D. S.,
RANDALL E. W.,
TATE K. R.
Publication year - 1984
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1984.tb00257.x
Subject(s) - pyrophosphate , chemistry , phosphorus , phosphate , soil water , fertilizer , lime , alkali metal , agronomy , zoology , environmental chemistry , organic chemistry , soil science , geology , biology , paleontology , enzyme
SUMMARY The different forms of phosphorus (P) in 0.5 m sodium hydroxide extracts of soils from long‐term field experiments at Rothamsted were characterized by 31 P‐nuclear magnetic resonance spectroscopy (NMR). The extract from an old grassland soil (pH 4.6) from a plot of the Park Grass Continuous Hay Experiment that had received no fertilizer or lime for at least 125 years contained the following forms of P: inorganic orthophosphate (22% of the extracted P), orthophosphate monoesters (49%), orthophosphate diesters (14%), phosphonates (3%), pyrophosphate (4%) and two unidentified forms of P (7%). The soil extract from a Park Grass plot given inorganic phosphate fertilizer (35 kg P ha −1 ) annually for 121 years contained the same forms of P and, in addition, a small amount of polyphosphate. There was also evidence of an increase in the orthophosphate monoester fraction. Another old grassland soil, of pH 6.1, contained more total and organic P than Park Grass but the extract contained fewer forms of P: inorganic orthophosphate (14% of the extracted P), orthophosphate monoesters (39%), orthophosphate diesters (34%) and an unidentified form (13%). An area of this grassland that had been ploughed up 20 years previously, and kept bare since, contained less organic P. The extract contained less of the phosphate diesters but the more stable monoesters remained relatively unchanged.