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Effect of long‐term combined nitrogen and phosphorus fertilizer application on 13 C CPMAS NMR spectra of humin in a Typic Hapludoll of northeast China
Author(s) -
Zhang J. J.,
Dou S.,
Song X. Y.
Publication year - 2009
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2009.01191.x
Subject(s) - humin , chemistry , fertilizer , alkyl , humic acid , magic angle spinning , nuclear magnetic resonance spectroscopy , nitrogen , phosphorus , organic chemistry , nuclear chemistry
Summary Because of its insolubility, heterogeneity and structural complexity, humin is the least understood among the three fractions of soil humic substances. This research aimed to evaluate the long‐term effect of combined nitrogen and phosphorus (NP) fertilizer addition on the chemical structure of humin under maize ( Zea mays L.) monoculture in a Typic Hapludoll of northeast China. Soil samples were collected 12 and 25 years after the initiation of the fertilizer treatment. Soil humin was isolated using NaOH‐Na 4 P 2 O 7 extraction to remove humic and fulvic acids, which was followed by HF‐HCl treatment to remove most of the inorganic minerals. Solid‐state 13 C cross‐polarization magic angle spinning nuclear magnetic resonance ( 13 C CPMAS NMR) spectroscopy was used to characterize the chemical structure of the humin isolates. Results showed that the organic carbon (C) content of humin increased after NP fertilizer addition, compared with a no‐fertilizer (CK) treatment. 13 C CPMAS NMR indicated that O‐alkyl C and aromatic C of humin decreased, while alkyl C and the ratios of alkyl C/O‐alkyl C, aliphatic C/aromatic C and hydrophobic C/hydrophilic C all increased in the NP fertilizer treatment. The long‐term application of NP fertilizer changed the molecular structure of soil humin to be more alkyl and hydrophobic, and was thus beneficial to the sequestration and stability of organic C in soil.