Phosphorus Speciation of Sequential Extracts of Organic Amendments Using Nuclear Magnetic Resonance and X‐ray Absorption Near‐Edge Structure Spectroscopies

• Published in: Journal of environmental quality 2007-11, Vol.36 (6), p.1563-1576
• Main Authors: Ajiboye, Babasola, Akinremi, Olalekan O., Hu, Yongfeng, Flaten, Donald N.
• Format: Article
• Language: English
• Subjects: Absorptiometry, Photon; Absorption; Agricultural wastes; Aluminum; Animal manures; Biosolids; Calcium; Cations - chemistry; Chemical extraction; Chemicals; Emission spectroscopy; Environmental impact; Litter; Magnetic Resonance Spectroscopy; Methods; Molecular Structure; NMR; Nuclear magnetic resonance; Organic Chemicals - chemistry; Organic phosphorus; Phosphates; Phosphorus - chemistry; Poultry; Soils; Speciation; Studies; Surface water; Swine
• ISSN: 0047-2425; 1537-2537; 1537-2537
• DOI: 10.2134/jeq2006.0541

The chemical forms of phosphorus in organic amendments are essential variables for proper management of these amendments for agro‐environmental purposes. This study was performed to elucidate the forms of phosphorus in various organic amendments using state‐of‐the‐art spectroscopic techniques. Anaerobically digested biosolids (BIO), hog (HOG), dairy (DAIRY), beef (BEEF), and poultry (POULTRY) manures were subjected to sequential extraction. The extracts and residues after extraction were analyzed by solution 31P nuclear magnetic resonance (NMR) and synchrotron‐based P 1s X‐ray absorption near‐edge structure (XANES) spectroscopies, respectively. Most of the total P analyzed by inductively coupled plasma– optical emission spectroscopy in the sequential extracts of organic amendments was orthophosphate, except POULTRY, which was dominated by organic P. The labile P fraction in all the organic amendments, excluding POULTRY, was mainly orthophosphate from readily soluble calcium and some aluminum phosphates. In the poultry litter, Ca phytate was the main P species controlling P solubility. The recalcitrant fraction of BIO was mainly associated with Al and Fe. Those of HOG, DAIRY, and POULTRY were calcium phytate, which were identified only as organic species in the XANES spectra. The combination of the three techniques—sequential chemical extraction, solution 31P NMR spectroscopy, and P 1s XANES—provided molecular characterization of P in organic amendments that would not have been possible with just one or a combination of any two of these techniques. Therefore, P speciation of organic amendments should use solid‐phase and aqueous speciation techniques as deemed feasible.