A COMPREHENSIVE APPROACH IN THE SEARCH OF MICROBIAL INDICATORS ASSOCIATED WITH DIFFERENT

GUERRERO, L.D.; AGARÁS, B.; REYNA, D.; GABBARINI, G.; DUVAL, M.; MARTINEZ, J.M.; FIGUEROLA, E.L.M.; FERRARI, A.; VALVERDE, C.; GALANTINI, J.; ERIJMAN, L.; WALL, L.G.

Seattle, WA, USA

Simposio; The 13th International Symposium on; 2010

International Society of Microbial Ecology

We present the first results of an interdisciplinary project (BIOSPAS) aimed at understanding how the microbial structure in soil under no-till farming are related to agricultural practices and soil properties. Three treatments were defined according to land use: 1) Sustainable agricultural management, subjected to intensive crop rotation and nutrient amendment, 2) Non-sustainable agricultural management with high mono-cropping without nutrient reposition, 3) Natural environment. Blocks of treatments were replicated 4 times in agricultural fields that had documented history of no-till management, at sites located across a west-east transect in Argentina's Pampas. Each sample was collected in triplicate, as a composite of 16 soil subsamples from 0-10 cm depth collected at 50 m intervals. The relative abundance of major taxonomic groups of bacteria was estimated using primer-specific quantitative PCR and PCR-DGGE. Pseudomonads were evaluated by quantifying the culturable fraction and by molecular markers oprF and gacA. Fatty acids profile, phosphatase and Glomaline Related Soil Proteins (GRSP) were also surveyed along with key soil variables (pH, moisture, organic carbon content, total nitrogen and P). Multivariate analysis was used to analyze microbial soil biology data. Differences in physicochemical and biochemical parameters were more consistently related to agricultural practices than bacterial community data. Principal component analysis separated soil management independently of site. Patterns of significant differences between treatments were obtained at the broad level of taxonomic resolution examined, but for most taxonomic groups the differences were site-specific. The results indicate that no-till systems support distinctive bacterial community composition and function according to land management, although the significance of these differences as indicators of soil quality requires further exploration.