Long-term fertilization modifies the structures of soil fulvic acids and their binding capability with Al

PLoS One. 2014 Aug 19;9(8):e105567. doi: 10.1371/journal.pone.0105567. eCollection 2014.

Abstract

The binding characteristics of organic ligands and minerals in fulvic acids (FAs) with Al are essential for understanding soil C sequestration, remain poorly understood. In this study, Fourier transform infrared (FTIR) spectroscopy combined with two-dimensional correlation spectroscopy (2DCOS) analysis was applied for the first time to explore the binding of Al with organic ligands and minerals in soil FAs. For these analyses, two contrasting treatments were selected from a long-term (i.e., 22-year) fertilization experiment: chemical (NPK) fertilization and swine manure (SM) fertilization. The results showed that the long-term application of organic and inorganic fertilizers to soils had little effect on the compositions of the fluorescent substances and organic ligands in the soil FAs. However, long-term SM fertilization increased the weathered Al and Si concentrations in the soil FAs compared with long-term chemical fertilization. Furthermore, organic ligands in the soil FAs were mainly bound with Al in the NPK treatment, whereas both organic ligands and minerals (Al-O-Si, Si-O) were bound with Al under the M fertilization conditions. Both transmission electron microscopy (TEM) images and X-ray diffraction spectra demonstrated that amorphous and short-range-ordered nanominerals were abundant in the soil FAs from the SM plot in contrast to the soil FAs from the NPK plot. This result illustrates the role nanominerals play in the preservation of soil FAs by during long-term organic fertilization. In summary, the combination of FTIR and 2D correlation spectroscopy is a promising approach for the characterization of the binding capability between soil FAs and Al, and a better understanding FA-Al binding capability will greatly contribute to global C cycling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aluminum / chemistry*
  • Animals
  • Benzopyrans / chemistry*
  • Carbon / chemistry
  • Carbon Sequestration / physiology
  • Fertilizers / analysis*
  • Ligands
  • Manure
  • Minerals / chemistry
  • Soil / chemistry*
  • Spectroscopy, Fourier Transform Infrared / methods
  • Swine
  • X-Ray Diffraction / methods

Substances

  • Benzopyrans
  • Fertilizers
  • Ligands
  • Manure
  • Minerals
  • Soil
  • Carbon
  • Aluminum
  • fulvic acid

Grants and funding

This work was funded by the National Natural Science Foundation of China (41371248, 41301241), the National Basic Research Program of China (2011CB100503), the Natural Science Foundation of Jiangsu Province of China (BK20131321, BK2013171), and the Qing Lan Project. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.