Origin and fate of soil lipids in a Phaeozem under rye and maize monoculture in Central Germany

摘要

Although soil lipids are an important class of soil organic substances, which is involved in numerous soil processes, their origin and fate in soils is insufficiently known. Therefore, this study aimed at investigating the free lipid fraction in crop residues and farmyard manure (FYM), and soils which received these materials for long time. We sampled rye and maize stubble and roots, FYM, and Ap horizon soils from the ‘Unfertilized’ and ‘FYM’ plots of ‘Eternal Rye Cultivation’ experiment at Halle, Saxony-Anhalt, Germany. Free lipids were extracted by dichloromethane/acetone and analyzed by gas chromatography/mass spectrometry. Aliphatics were most abundant in all extracts, accounting for 61 to 77% of the total extractable lipids. By comparing the lipid composition of the added organic materials with that of the corresponding treated soil, the long-chain members of n-alkanols, n-alkanes, α,ω-alkanedioic acids, and unsaturated alkanoic acids from C16 to C19 did not disappear in soil whereas ω-hydroxyalkanoic acids and long-chain branched alkanoic acids were not extracted from soil probably because they were bound to nonextractable forms. It is suggested that the methodological approach can give information on decomposition and retention of free extractable lipids in soil. More information is needed to trace the fate of all lipids in the plant–soil system by the determination of bound molecules, which are nonextractable by organic solvents.