Identification of soil organic phosphorus by P-31 nuclear magnetic resonance spectroscopy

Soil samples from different land use systems were collected before cropping (in spring) and after harvest (in fall) for organic phosphorus (P) extract ions by 0.4M sodium hydroxide (NaOH) and characterization by P-31 nuclear m agnetic resonance spectroscopy. To prevent hydrolysis of organic P compound s prior to sample concentration, NaOH was removed from the NaOH soil extrac ts using a G-25 Sephadex column. The P-31 NMR spectra in the NaOH soil extr acts showed the presence of glucose-6 phosphate (up to 64%), glycerophospha te (up to 45%), nucleoside monophosphates (up to 91%), and polynucleotides (up to 58%) as the major forms of organic P in soils. The relative concentr ation of nucleoside monophosphates and polynucleotides decreased in some of the soils after harvest. The 31P NMR spectra of the extracts also revealed the presence of phosphoenolpyruvates, a previously unreported form of soil organic P.