02294nam a2200277 a 450000100080000000500110000800800410001910000210006024500860008126000450016730000100021250000180022252015450024065000120178565000170179765000170181465000190183165000140185065000130186465000220187765000260189965000180192565000270194365000280197065300180199815570922010-10-07       1997    bl uuuu  m   00u1 u    #d1 aMENDES, I. de C.  aMicrobiology of soil aggregates recovered from different crop management systems.  aCorvallis: Oregon State Universityc1997  a138p.  aPh.D. Thesis.  aMy thesis research examined the relationship between soil structure and soil microorganisms. I examined the distribution of microbial biomass and its activities across soil aggregates and also the distribution across aggregates of a specific soil bacterium, Rhizobium leguminosarum bv trifolii. These distributions were evaluated in a summer vegetable cropping system in which three winter cover-crop treatments are practiced (fallow; cereal and legume). Five aggregate size classes (&lt0.25, 0.25 to0.5, 0.5 to 1.0, 1.0 to 2.0 and 2.0 to 5.0 mm) were obtained from each treatment by a dry sieving procedure. The distributions of total organic C (TOC), total Kjeldahl N (TKN), total soil bacterial population, microbial biomass C (MBC), mineralizable C and N (Min.C and Min.N), and two enzyme activities (B-glucosidase, FDA-hydrolysis) were measured after cover crop incorporation at seedbed preparation (June), and after harvest of the sweet-corn or broccoli summer crop (September). Immunofluorescence direct count microscopy (IFDC) and the plant infection soil dilution technique (MPN) were used to examine the seasonal distribution of R. leguminosarum bv trifolii across the same soil aggregate preparations. Despite the cover crop treatmens having been in place for seven years, they have not influenced the overall level of TOC, TKN, and aggregate size distribution. Cover crop effects on microbial soil interactions were subtle, often being seen at specific sampling  times and interacting with aggregate size. Rhizobium serotype ...  abiomass  amicrobiology  asoil biology  asoil structure  aBactéria  aBiomassa  aEstrutura do Solo  aMicrobiologia do Solo  aMicrorganismo  aPopulação Microbiana  aRhizobium Leguminosarum  aMicrorganisms