Extractable lipids and organic matter status in two soil catenas as influenced by tillage

Tillage practices and soil texture can influence the dynamics of soil organic matter (SOM) transformations, so that direct indicators of SOM quality are needed to assess its biological, chemical and physical functions. A field study was conducted to investigate the characteristics of diethyl ether (DEE) and chloroform (CHCl3) extractable lipids following a three-year rotation of maize, soybean and winter wheat on a Gray Brown Luvisol and a Humic Gleysol of two soil catenas. The mass spectrometric data showed that n-fatty acids, n-alkyl benzenes, alkanes, alkenes, unsaturated n-alcohols, and n-alkyl mono- and di-esters were the most abundant organic molecules in the two soil catenas. The extracts of no-till soil samples were rich in n-fatty acids compared to conventionally-tilled soil samples, and soil samples from Catena 2 contained unsaturated n-alcohols, which were absent in soil samples from Catena 1. Principal component analysis (PCA) showed that the molecular composition and the quantitative values of the extractable lipids were highly sensitive indicators of the quality of SOM in coarse and fine textured soils under no-till and conventional tillage. (C) 1998 Elsevier Science B.V. All rights reserved.