EXTRACTABLE LIPIDS AND ORGANIC-MATTER STATUS IN 2 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 fu nctions. A field study was conducted to investigate the characteristic s of diethyl ether (DEE) and chloroform (CHCl3) extractable lipids fol lowing a three-year rotation of maize, soybean and winter wheat on a G ray Brown Luvisol and a Humic Gleysol of two soil catenas. The mass sp ectrometric 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 extr acts of no-till soil samples were rich in n-fatty acids compared to co nventionally-tilled soil samples, and soil samples from Catena 2 conta ined unsaturated n-alcohols, which were absent in soil samples from Ca tena 1. Principal component analysis (PCA) showed that the molecular c omposition and the quantitative values of the extractable lipids were highly sensitive indicators of the quality of SOM in coarse and fine t extured soils under no-till and conventional tillage. (C) 1998 Elsevie r Science B.V. All rights reserved.