Aporte de fitomassa pelas sucess？es de culturas e sua influência em atributos físicos do solo no sistema plantio direto

soil physical degradation, like compaction, reduces water movement and root development. soil structure is considered one of most importance to agriculture and closely related to it are other fundamental properties in soil-plant relationship. the objective of this study was to evaluate the effect of crop sequences on physical attributes. the research was realized in 2004/05 and 2005/06 growing seasons, in a typic clayey rhodic hopludox, under eight years of no-tillage system, at dourados (ms). the experiment was a randomized complete block design, with three replications. treatments were constituted by cover crops: sunflower (helianthus annuus l.), sunnhemp (crotalaria juncea l.), hairy vetch (vicia villosa roth), mixture of sunnhemp + black oat (avena strigosa schreb), and mixture of black oat + hairy vetch + oilseed radish (raphanus sativus l. var. oliferus metzg). differences were not observed in soil density, porosity and aggregation rate when it was cultivated with sunflower, hairy vetch, sunnhemp, or the mixtures. differences were observed in soil physical properties between 0-5 cm layer and 5-10cm - 10-20 cm layers, but no differences between 5-10 cm and 10-20cm layers. soil carbon trend to higher contents in crops with high production of surface residues, although differences in carbon contents were insufficient to modify aggregation.