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Evidence from nuclear magnetic resonance spectroscopy of the processes of soil organic carbon accumulation under long‐term fertilizer management
Author(s) -
Xu J. S.,
Zhao B. Z.,
Chu W. Y.,
Mao J. D.,
Olk D. C.,
Zhang J. B.,
Wei W. X.
Publication year - 2017
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/ejss.12445
Subject(s) - fertilizer , chemistry , soil carbon , magic angle spinning , agronomy , phosphorus , potassium , nuclear magnetic resonance spectroscopy , soil water , soil science , stereochemistry , organic chemistry , environmental science , biology
Summary Long‐term application of fertilizers has a considerable effect on the accumulation of soil organic carbon ( SOC ), but the underlying processes remain unclear. We have examined the effects in the soil of two long‐term (> 20 years) field experiments of a double‐cropped maize ( Z ea mays L .)–wheat ( T riticum aestivum L .) rotation on a C alcaric F luvisol and paddy rice ( O ryza sativa L ) on a H ydragric A nthrosol. The chemical structures of the SOC were characterized with multiple cross‐polarization magic‐angle spinning 13 C nuclear magnetic resonance spectroscopy. The treatments included organic fertilizer ( OF ) only, combined NPK (nitrogen, phosphorus and potassium) fertilizer with OF ( NPKOF ), mineral fertilizer pairings of NPK , NP and NK , and an unamended control. The continuous fertilizer treatments did not change the chemical composition of the A nthrosol SOC greatly except that the NPKOF treatment slightly enriched aromatic C and depleted O –alkyl C compared with the C ontrol. All the treatments on the A nthrosol soil resulted in SOC accumulation, but to different extents. Principal component analysis of the A nthrosol and F luvisol showed different relationships between the soil properties and functional groups. The F luvisol SOC decreased in the order balanced fertilizer treatments ( OF , NPKOF and NPK ), NP , Control and NK treatments. The main structural changes of the F luvisol SOC followed the same order with a decrease in the abundance of aromatic C O , aromatic C , anomeric C , O –alkyl C and OCH 3 / NCH , and an increase in COO / N C O and alkyl C , which led to an increase in alkyl– C/O –alkyl– C ratios and a decrease in aromaticity values. These results suggest that SOC accumulation with balanced fertilization on the F luvisol can be attributed to less decomposition and more humification of the organic materials, whereas the smallest SOC content associated with P omission can be ascribed to more complete decomposition to gaseous end products. We consider that the chemical compositions of SOC may be altered by long‐term fertilizer treatments, depending on the soil type. Highlights How does soil organic carbon ( SOC ) change in response to long‐term fertilizer management? Improved understanding of SOC accumulation in F luvisol and A nthrosol agricultural soils. Phosphorus omission in the F luvisol retarded the accumulation and stimulated the decomposition of SOC . Fertilizer treatments affected chemical composition of SOC of the F luvisol, but not the A nthrosol.