Soil conservation practices are critical for agricultural sustainability, and in this study the shotgunsequencing approach was used to investigate the effects on soil biodiversity of different soil- andcrop-management practices in a 13-year field trial in southern Brazil. Treatments consisted of conven-tional tillage (CT) with plowing and disking, or no-tillage (NT) with direct sowing into the residues ofprevious crops, in a crop succession [soybean (summer)/wheat (winter)] or rotation [soybean/maize(summer)/wheat/lupine/oat (winter)]. About 1 million reads per treatment revealed very high levels ofdiversity. The majority of the sequences were attributed to the Bacteria (54%), and 0.3% and 0.2% fittedinto Archaea and Eucarya domains, respectively; 46% showed no similarity with any known sequences.Major differences were associated with tillage and, to a lesser extent, with crop management. Statisticallysignificant higher abundances with CT encompassed microorganisms associated with residue decompo-sition, carbon and nitrogen cycling, and xenobiosis. Eucarya were also more abundant with CT, possiblyrelated to higher tolerance of environmental stresses. In contrast, NT showed higher abundances par-ticularly of nitrogen-fixing Rhizobiales and Archaea that inhabit environments rich in organic matter.2013