02939naa a2200313 a 450000100080000000500110000800800410001910000140006024501170007426000090019152020550020065000210225565000150227665000190229165000090231065000240231965000120234365000230235565000090237865300220238765300170240965300190242665300210244570000190246670000200248570000200250570000210252577300790254610297922006-04-11       2000    bl ---       0--  u    #d1 aBAYER, C.  aOrganic matter storage in a sandy clay loam Acrisol affected by tillage and cropping systems in southern Brazil.  c2000  aSoil organic matter decline and associated degradation of soil and environmental conditions under conventional tillage in tropical and subtropical regions underline the need develop sustainable soil management systems. This study aimed first to evaluate the long-term effect (9 years) of two soil-tillage systems (conventional tillage: CT, and no-tillage: NT) and two cropping systems (oat (Avena strgosa Schreb)/maize (Zea mays L.): O/M; and oat+common vetch (Vicia sativa L.)/ maize+cowpea (Vigna unguiculata (L.) Walp): O+V/M+C without N fertilization on total organic carbon (TOC) and total nitrogen (TN) concentrations in a sandy clay loam Acrisol in southern Brazil. The second objetive was to asses soil potential for acting as an atmospheric CO2 sink. Under NT an increase of soil TOC and TN concentrations occured, in both cropping systems, when compared with CT. However, this increase was restricted to soil surface layers and it was higher for O+V/M+C than for O/M. The O+V/M+C under NT, which probably results in the lowest soil organic matter losses (due to erosion and oxidation) and highest addition of crop residues, had 12 Mg ha-1 more TOC and 0.9 Mg ha-1 more TN in the 0-30.0 cm depth soil layer, compared with O/M under CT which exhibits highest soil organic losses and lowest crop residue additions to the soil. These increment represent TOC and TN accumulation rates of 1.33 and 0.10 Mg ha-1 per year, respectively. Compared with CT and O/M, this TOC increase under NT and O+V/M+C means a net carbon dioxode removal of about 44 Mg ha-1 from the atmosphere in 9 years. NT can therefore be considered, as it is in temperate climates, an important management strategy for increasing soil organic matter. In the tropical and subtropical, where climatic conditions cause intense biological activity, in order to maintain or increase soil organic matter, improve soil quality and contribute to mitigation of CO2 emmisions, NT should be associated with cropping systems resulting in high annual crop residue additions to soil surface.  acropping systems  ano-tillage  aorganic matter  asoil  asoil organic matter  aLavoura  aMatéria Orgânica  aSolo  aSistema de semear  aSoil tillage  aSustainability  aSustentabilidade1 aMIELNICZUK, J.1 aAMADO, T. J. C.1 aMARTIN-NETO, L.1 aFERNANDES, S. V.  tSoil & Tillage Research, Amsterdamgv. 54, n. 1/2, p. 101-109, Marc. 2000.