Spectroscopy and Spectral Analysis, Volume. 38, Issue 3, 958(2018)
Molecular Speciation of Phosphorus in an Organically Bound Phosphorus Fertilizer with High Phytoavailability Characterized by Multiple
While the global phosphorus (P) resources is running low, the environmental issues due to over-application of P fertilizers become increasingly urgent. There is a more pressing need than ever before to develop new types of P fertilizers with high phytoavailability with agronomic, environmental and sustainability benefits. Compared to generally applied inorganic P fertilizers, organically bound P fertilizers are less prone to soil fixation, and could remain relatively high mobility from where the fertilizer is added to the rhizosphere for crop utilization. Developing organically bound P fertilizers is increasingly recognized as an efficient way to fundamentally solve the current problem induced by the low phytoavailability of inorganic P fertilizers. In recent few years, related studies are becoming popular, but researches on the speciation of the emerging organically bound P fertilizers are not well-documented until now. Various organically bound P fertilizers were developed and their P phytoavailability were tested. Our previous study showed that the starch-bound P fertilizer had high P efficiency. Since the phytoavailability of P fertilizers was a function of the P species present in the fertilizer and the transformations in soils after application, this current study probed P speciation in the starch-bound P fertilizer at the molecular level by solution P-31 nuclear magnetic resonance (P-NMR) and synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy. To obtain quantitative results by P-NMR analysis, the fertilizer sample was hydrolyzed to α-limited dextrin, and then dissolved with dimethyl sulfoxide solution (45%). Nicotinamide adenine dinucleotide was added as an internal reference standard. It indicated that the total P concentration in the studied fertilizer by NMR agreed with that by the colorimetric chemical method. Phosphorus in the starch-bound P fertilizer was mainly presented as orthophosphate monoester, representing 75.8% of total P. Orthophosphate diester accounted for 17.3% of total P, while inorganic P only 6.9%. Furthermore, the XANES spectra of the P fertilizer closely resembled that of phytic acid, and was lack of the characteristic features of inorganic P species. Conclusively, these results illustrated the dominance of organic orthophosphate monoester in the studied fertilizer. Combining state-of-the-art of spectroscopic analysis, this study provides an important basis for further studies on the high phytoavailability mechanisms of organically bound P fertilizers.
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LIU Jin, YANG Jian-jun, Yongfeng HU, LI Ju-mei, ZHANG Xiu, MA Yi-bing. Molecular Speciation of Phosphorus in an Organically Bound Phosphorus Fertilizer with High Phytoavailability Characterized by Multiple[J]. Spectroscopy and Spectral Analysis, 2018, 38(3): 958
Received: Jun. 4, 2017
Accepted: --
Published Online: Apr. 9, 2018
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