Journal of
Soil Science and Environmental Management

  • Abbreviation: J. Soil Sci. Environ. Manage.
  • Language: English
  • ISSN: 2141-2391
  • DOI: 10.5897/JSSEM
  • Start Year: 2010
  • Published Articles: 287

Full Length Research Paper

Composition and structure of humic substances in long-term fertilization experimental soils of southern China

Bocar Ahamadou1*, Qiaoyun Huang2, Lin Yaping2 and Javed Iqbal3
1Unit of Soil Science, Department of Agronomy, Katibougou Rural Polytechnical Institute of Training and Applied Research, P. O. Box 06 Koulikoro, Mali. 2Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, 430070, P.R. China. 3Department of Plant and Soil Science, 2207 Agronomy Hall, Iowa State University, Aames IA, 50010, USA.
Email: [email protected]

  •  Accepted: 30 July 2013
  •  Published: 31 August 2013

Abstract

Humic substances are extremely important attributes of soil quality but the impacts of long-term fertilization on their composition and structure remain controversial and are still not fully understood. A study, employing various methods was conducted to elucidate the influence of long-term fertilization practices on the composition and structure of humic substances. Soil samples were collected from eight treatments at the Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences. Data were subjected to analysis of variance (ANOVA), using the MSTAT-C software package. In general, the Fourier transform-infrared (FT-IR) spectra discriminated bands between humic fractions. The humic acid (HA) from the NPK plus manure (NPKM) and manure alone (M) treatments showed higher values of the O/R ratios (1.24 and 1.18, respectively) as compared to that from the 1.5 NPKM and fallow (H) treatments, which decreased these ratios (0.66 and 0.85, respectively). Except for NPKM plus wheat-soybean-sweet potato between the lines (NPKMR), the O/R ratios of the fulvic acid (FA) did not differ among the treatments. However, the humin (HM) from H and the control (CK) displayed the highest value of O/R ratios (about 3.23 for both). Humic substances from organic treatments showed more aliphatic nature, whereas more condensed-alkali soluble humic substances were formed in the unfertilized and mineral treatments. Among fractions, the HA formed more phenolic or aromatic structures than did the FA or HM. In addition, the C, H, N and S contents of humic substances increased significantly, whereas their oxygen content decreased.

 

Key words: Long-term fertilization, soil quality, humic substances, Fourier transform-infrared (FT-IR) spectroscopy, elemental composition.