Organic compounds at different depths in a sandy soil and their role in water repellency

• DOI: 10.1071/sr04094
• Publication Date: 2005-05-27T01:29:26Z
• Authors: C. P. Morley; K. A. Mainwaring; S. H. Doerr; P. Douglas; C. T. Llewellyn; L. W. Dekker
• Keywords: Topsoil; Subsoil; Wettable powder; Soil test

The causes of soil water repellency are still only poorly understood. It is generally assumed that hydrophobic organic compounds responsible, but those concerned have not previously been identified by comparison between samples taken from a repellent topsoil and the wettable subsoil. In this study we separated, characterised, compared present at 4 different depths in sandy under permanent grass cover upper 0.30 m below this. Soil were extracted using mixture isopropanol aqueous ammonia (7 : 3 v v). Samples after extraction re-application extract each sample onto sand induced repellency. chloroform-soluble portions extracts analysed gas chromatography chromatography-mass spectrometry. all included long-chain carboxylic acids (C16–C24), amides (C14–C24), alkanes (C25–C31), aldehydes or ketones (C25–C29), more complex ring-containing structures. 1H 13C nuclear magnetic resonance spectroscopy, carbon/hydrogen ratio as determined microanalysis, confirmed predominantly aliphatic character extracts. Both contained compounds. far material, although amount was related to degree Perhaps importantly, they polar high relative molecular mass, which almost absent may be speculated these whose presence significant amounts necessary for exhibited.