Bacterial diversity and soil physiology dynamics in no-till agriculture soils under different managements

FIGUEROLA ELM; FERRARI A; GABBARINI L; FRENE JP; REYNA D; ERIJMAN L; WALL LG

Simposio; BAGECO 12 (12th Symposium on Bacterial Genetics and Ecology); 2013

No-till is a conservation farming practice adopted in several parts of the world to cope with soil erosion, increase carbon storage and make a more efficient use of available moisture. However, farmers? experience suggests that reduced tillage needs to be coupled with crop rotation and good agrochemical management to be sustainable. Samples were obtained in Summer and Winter during 2010 and 2011 in no-till soils managed with two contrasting practices (high or low crop rotation), and a grassland as control (3 treatments), replicated in four geographical sites (4 different soil textures) located across a regional scale of 400 km in the Argentinean Pampas (3 subsamples for each case). For the comparison of the bacterial community structure a fragment of the v4 region of 16S rRNA gene was high-throughput sequenced. Soil physiology was studied by: FAME analysis of Phospho and Neutral fractions of soil lipids; characterization of Physiological Profile at the Community Level (CLPP) using substrate induced respiration, characterization of Phosphatase activity, and estimation of Glomalin related soil proteins. > 150,000 16S rRNA gene sequences were obtained for a total of 108 samples. We did not find significant differences in bacterial diversity that can be related to sites or soil management. However, there are phylogenetic differences between samples, which can be explained on the basis of both geographical location and agricultural management. Fame analysis shows that PLFA separates samples geographically while NLFA does it by soil treatments. Branched chain FA/PUFA and MUFA/PUFA ratios of Neutral Lipids discriminate agricultural practices. FAs 20:0 and 18:1w7c appear to be markers for different soil managements independently of the season. CLPP analyses show a sharp discrimination between different soil treatments being clearer in winter samples. Phosphatase activity analyses show equal results although discrimination between treatments was better in summer samples. Glomaline related soil proteins show different variations according to soil management depending on the soil texture or environment. The integration of all these data will give the basis to learn how to maintain the sustainability of agricultural soil ecosystems and to find biomarkers for diagnosis of soil quality within the Pampa region.