Characterization of no- till soils under different agricultural management by analysis of whole cell fatty acids

FERRARI A; WALL LG

Rosario

Congreso; 7th World Congress on Conservation Agriculture; 2017

CAAPAS-AAPRESID

Analysis of whole cell fatty acids (WCFA) was used to characterize no-till productive agricultural soils associated with different crop rotation intensity in the Argentinean pampas, during two sampling seasons. High crop rotation (HR) treatment consisted in maize-wheat-soybean intense rotation including cover crops. Monoculture (MC) treatment consisted on low rotation intensity with trend to soybean monocultures. Soils from nearby natural environments (NE) were used as references. These agricultural systems were recently studied by the more complex PLFA method, which separated lipid in phospholipid, glycolipid and neutral lipid fractions. The objectives of this work were to find lipid-based markers of agricultural management by using the simpler, cheaper and more sensitive WCFA technique.NE sites had higher total concentration of WCFA than the agricultural sites, with no difference between CR and MC. NE sites were also characterized by straight chain and mono-unsaturated fatty acids like 16:1w5c, a known arbuscular mycorrhizal biomarker. Comparing lipid profiles by multivariate methods, the CR and NE sites were more alike between them than with MC sites, with several fatty acids in common. This fact suggests that the CR management conserves soil microbial diversity in a larger scale than MC treatment does.The WCFA 16:03OH, a marker of Gram-negative bacteria, showed a significant trend in the direction NE>CR>MC in both sampling seasons. This result is in agreement with the PLFA technique, working with the same samples set. Some rare or less known fatty acids like 15:1isoG and 15:0iso3OH were also associated to CR treatments, both in this work (WCFA technique) and with the PLFA method, suggesting fatty acids in the unculturable soil pool. Using the WCFA technique, and not in the PLFA method, we found that 18:1w7c was always higher in MC that in CR sites, suggesting a potentially new marker of less intense rotations in agriculture.In conclusion, the simpler and faster WCFA technique has reached a similar characterization of the soil microbial biota than the more complex PLFA technique, also proposing some new markers of high crop rotation agriculture, being the Gram-negative bacteria apparently the most sensitive microbial taxa under two different no-till managements.