03268naa a2200265 a 450000100080000000500110000800800410001910000190006024501570007926000090023652024290024565000250267465000150269965000210271465000200273565000190275565000190277470000180279370000220281170000250283370000150285870000180287370000170289177300940290816582442017-08-31       2009    bl ---       0--  u    #d1 aBARRETO, R. C.  aThe impact of soil management on aggregation, carbon stabilization and carbon loss as CO2 in the surface layer of a Rhodic Ferralsol in Southern Brazil.  c2009  aSoil aggregation and organic carbon accumulation are two intrinsically linked phenomena. Soils under natural vegetation and conservation tillage systems generally have higher aggregation indices and total organic carbon (TOC) stocks in the surface layers than soils under conventional management (ploughing). Fromthe point of viewof the emission of carbondioxide (CO2), C stabilization and loss in the surface layer is relevant. The objective of this study was to investigate the effect of no-tillage (NT) and conventional tillage (CT) on TOC stabilization and loss through soil aggregation in the topsoil. Soil aggregation, TOC stocks, and fluxes of CO2 of samples from a Rhodic Ferralsol under NT and CT in a long-term field experiment in Southern Brazil were measured. A natural forest site was also evaluated as reference to the management sites.Emissions ofCO2weremeasured in laboratory incubation experiment on bulk soilsamples and on soil aggregate size fractions, previously separated by dry sieving, in intact and destroyed (crushed to &lt0.250 mm) state. The soil under NT had larger aggregates and larger proportion of the soil in greater aggregate size classes than CT. Total organic carbon stocks were higher under NT both in bulk soil samples and macroaggregates than under CT. Under laboratory conditions the bulk soil samples from NT showed higher emission rates of CO2 (CO2BS = 18.3 kg C ha-1 h-1) than from CT (CO2BS = 2.3 kg C ha-1 h-1) due to the overall higher TOC stocks. The TOC that was lost by CO2 emission due to the oxidation of readily decomposable macroaggregate-protected SOM in NT (SDCO2 = 79.4 kg C ha-1 h-1) was, however, also higher than under CT (CT:SDCO2 = 29.1 kg C ha-1 h-1). TheTOCstabilized bymacroaggregation inNTwas also more than the TOC lost by CO2 emission from the bulk soil (SDCO2-CO2BS = 61.1 kg C ha-1 h-1), and the difference between these two washigher underNTthan under CT (SDCO2-CO2BS = 26.8 kg C ha-1 h-1), showing that NT in fact accumulates more TOC in the soil by protecting it within themacroaggregates. The natural forest had higher TOC stock and emission rates than the tilled soils, however it also stabilized more TOC. Thus, no-tillage in its effect on carbon stabilization, is between the natural ecosystem and CT, representing a soilmanagement system that seemsto be an efficient on thewaypath to the recuperation of soil after conventional management systems.  aconventional tillage  aNo-tillage  aSoil aggregation  aSoil management  aManejo do solo  aPlantio direto1 aMADARI, B. E.1 aMADDOCK, J. E. L.1 aMACHADO, P. L. O. A.1 aTORRES, E.1 aFRANCHINI, J.1 aCOSTA, A. R.  tAgriculture, Ecosystems & Environment , Amsterdamgv. 132, n. 3-4. p. 243-251, ago. 2009.