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

Abstract

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 (31)P 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 (31)P 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.

Characterizing Fecal and Manure Phosphorus from Pigs Fed Phytase Supplemented Diets

“…Similar overestimation of inorganic P in H 2 O-P has been reported by other authors (Ajiboye et al, 2004(Ajiboye et al, , 2007. However, while Ajiboye et al (2004Ajiboye et al ( , 2007 determined organic P as the difference between P measured by the inductively couple plasma atomic emission spectroscopy (ICP-AES) and molybdate blue method, organic P in this study was determined as the difference between molybdate blue measured P in digested and undigested P extract. Acid digestion of extract and the subsequent neutralization of the digest for molybdate blue P determination could also interfere with P measurement in the digested sample especially if the concentration of organic P is very low.…”

“…Inorganic P (NaOH-Pi) constituted between 16 and 61% of P extracted by NaOH in the feces, and between 26 and 69% of P extracted in the manure. Turner and Leytem (2004) reported 59% of hog manure NaOH-P as inorganic while Ajiboye et al (2007) reported 79% as inorganic P. The wide variation in percent NaOH-Pi among the various dietary treatments was due to the presence or absence of supplemental inorganic P with NaOH-Pi decreasing with decreasing supplemental inorganic P (Table 4). It is possible that inadequate supply of P prevented the reaction of phosphate with cations such Al, Ca, Mg and Fe.…”

“…Turner and Leytem (2004) reported that inorganic P accounted for more than 96% of H 2 O-P from swine manure. Ajiboye et al (2007) complemented sequential extraction with nuclear magnetic resonance (NMR) spectroscopy to confirm that H 2 O-P from sequential extraction of hog manure was mostly in the inorganic form.…”

“…As was observed with H 2 O-P, the percent inorganic P in some NaHCO 3 extracts of feces was greater than 100% resulting in negative values of the organic P. About 95 to 99% of manure NaHCO 3 -P was in inorganic P form. Ajiboye et al (2007) reported that P extracted by NaHCO 3 was mainly inorganic P.…”

Spectroscopic quantification of soil phosphorus forms by 31p-nmr after nine years of organic or mineral fertilization

“…This shows that even in the organic fertilizer treatments, P was accumulated mainly in inorganic forms, due to the high inorganic P levels that are already present in animal manures (Cassol et al, 2001;Koopmans et al, 2003;McDowell & Stewart, 2005) or because of the rapid enzymatic hydrolysis after soil application (He et al, 2008). Ajiboye et al (2007) showed that in alkali extract of cattle manure, 92 % of total P belonged to the orthophosphate category and only 5 % to monoester and 3 % to the diester category. In poultry litters, orthophosphate accounted for only 43 % of total P, monoester for 51 % (47 % in phytic acid) and diester for only 6 %.…”