Crop rotation in no-till soils modifies the soil fatty acids signature

Abstract

Analysis of whole-soil fatty acids (WSFA) was used to characterize no-till productive agricultural soils associated with different crop rotation managements on the Argentinean pampas, over two sampling seasons. Crop rotation (CR) treatment was compared with soybean monocropping (MC). Soils from nearby natural environments (NE) were used as reference treatments. The objective of this study was to characterize the soil lipid signature and seek putative markers of agricultural management. NE sites had greater concentration of total WSFA than agricultural sites, but no differences between CR and MC were identified. NE sites were characterized by straight chain and mono-unsaturated fatty acids, such as 16:1ω5c, an established biomarker for arbuscular mycorrhiza. Comparing lipid profiles using multivariate methods allowed a comprehensive comparison among treatments. The CR and NE soil samples were more alike than those of MC, with several fatty acids in common. CR soils were associated with mixed, branched and hydroxylated fatty acids. MC profiles appeared to be enriched by 16:010Me and 18:1ω7c fatty acids, which could be potential treatment markers. Thus, use of the WSFA approach to study soil lipid signature appeared to be a sensitive method to characterize soil health and soil use and management. However, some of the fatty acids do not come from living cells but from soil organic matter, which sets a limitation on interpretation in terms of the microbial community but expands the biological origin of the soil lipid signature to any biological matter, alive or death, which is a constitutive part of the soil under study.