Horizon 1 1 17 ACLN : Articles dans des revues avec comité de lecture non répertoriées par l'AERES Plant and Soil 243-255 BIOLOGIE DU SOL BACTERIE NUMERATION VERTISOL BIOMASSE HERBACEE DENSITE DE POPULATION AGREGAT 1994 fdi:010013328 ENG Plant and Soil 0032-079x 2 10.1007/BF00007974 https://www.documentation.ird.fr/hor/fdi:010013328 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_6/b_fdi_49-50/010013328.pdf 163 Horizon (IRD) Effects of soil management on soil characteristics were investigated on the rhizosphere (RPP) and the non-rhizosphere (NRPP) siol of a re-grass vertisol under #Digitaria decumbens$ and in the soil under continuous cultivation (CC). A low energy technique allowed to separate eight size and density fractions, including macro- and micro-aggregates while preserving soil bacteria. Organic C and N, microbial biomass C and the number of total bacteria (AODC) and of #Azospirillum brasilense$ and their distribution were determined in soil fractions isolated from the CC, NRPP and RPP soils. Soil macroaggregates (>2000 micrometers) were similarly predomminant in the NRPP and RPP soils when the dispersible clay size fraction (<2 micrometers) represented more than 25% of the CC soil mass. The main increase of C content in RPP originated from the macroaggregates (>2000 micrometers) and from the root fraction, not from the finer separates. The proportion of organic C as microbial biomass C revealed the low turnover of microbial C in the PP situations, especially in the clay size fraction of the NRPP soil. A common shift of AODC toward the finer separates from planted soils (CC and RPP) revealed the influence of living plants on the distribution of soil bacteria. The relative abundance of #A. brasilense$ showed the presence of the active roots of #Digitaria$ in the macroaggregates and their contact with the dispersible clay size fraction of the rhizosphere soil. (Résumé d'auteur) 074MICFLO01