Pedosphere 25(3): 372--385, 2015
ISSN 1002-0160/CN 32-1315/P
©2015 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| UV/Vis characterization and fate of organic amendment fractions in a dune soil in Dakar, Senegal |
S. DAOUK1 , M. HASSOUNA1, A. GUEYE-GIRARDET1, S. NIANG2 and H.-R. PFEIFER1 |
1Institute of Earth Sciences, Faculty of Geosciences and Environment (FGSE), University of Lausanne, 1015 Lausanne (Switzerland)
2Laboratory of Wastewater Treatment, Fundamental Institute of North Africa (IFAN), Cheikh Anta Diop University of Dakar, BP 5005 Dakar (Senegal) |
| ABSTRACT |
| The application of organic amendments on soils poor in organic matter (OM) can improve long-term soil fertility, but may also enhance the mineralization of native soil organic matter. Three organic amendments, compost, sewage sludge and horse manure used by urban market gardeners in Dakar, Senegal were analyzed for their OM maturity. Their fate was evaluated in a 45-d agronomic trial in a sandy Arenosol with lettuce. In each case, water-extractable organic matter (WEOM) and humic-like substances (HLS) were isolated from raw amendments and amended soils, and characterized using ultraviolet-visible (UV/Vis) spectroscopy. Results highlighted the general more aromatic character of HLS and WEOM fractions extracted from compost compared to the other two amendments. When applied to soils, however, these differences were not clearly observed. The aromaticity and humification degree of the labile fraction (WEOM) increased with depth in the first 30 cm for all amendments. This indicated the high lixiviation rates that fresh OM underwent in the studied sandy soil. Finally, a statistical analysis of the results was able to discriminate between surface and deeper horizons and between amended- and non-amended soil samples. Spectroscopic indices showed indeed strong increase/decrease with depth linked with the mineralization/humification processes that the fresh OM from amendments underwent during the 45 d of the agronomic trial. This study highlights the potential of spectroscopic techniques to study agricultural amendment organic matter fractions and their fate in soils. |
| Key Words: absorbance spectroscopy, compost, fluorescence spectroscopy, horse manure, humic-like substances, sewage sludge, water-extractable organic matter |
| Citation: Daouk, S., Hassouna, M., Gueye-girardet, A., Niang, S. and Pfeifer, R. 2015. UV/Vis characterization and fate of organic amendment fractions in a dune soil in Dakar, Senegal. Pedosphere. 25(3): 372-385. |
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