Sabine Ravnskov

Analysis of phospholipids (PLFA) and neutral lipids fatty acids (NLFA) was used to characterizeno-till productive agricultural soils associated with different crop rotation levels, replicated across a400 km transect in the Argentinean pampas, during two sampling seasons, summer and winter. Highrotation (HR) management consisted in maize–wheat–soybean intense rotation including cover crops.Low rotation (LR) management trend to soybean monocultures. Soils from nearby naturalenvironments (NEs) were used as references. Fatty acids concentration in soils (nmol/g) decreased c.a.50% from summer to winter differentially according to soil treatment being the smallest decrease inHR management 35%. Both PLFA and NLFA profiles showed strong potential to discriminatebetween different land uses. In winter samples, some rare or unknown fatty acids were relevant forthe discrimination of agricultural practices while NLFA 20:0 appears to be a good marker of HRsoils despite season or location. The PLFA-based taxonomic biomarkers for total bacteria, Gramnegativebacteria and arbuscular mycorrhiza showed a significant trend NE>HR>LR in the wintersampling. HR management was also characterized by high levels of NLFA in winter samples as ifhigh crop rotation improves lipids reserves in soil during winter more than in monocropping soilmanagement. In conclusion, PLFA and particularly NLFA profiles appear to provide useful andcomplementary information to obtain a footprint of different soil use and managements, improvingsoil biochemistry characterization tools.