The effect of physical, chemical and biological soil attributes on the stability of wet aggregates of two Oxisols cultivated with annual crops under no tillage for over four years was evaluated. Soils samples were collected in the 0-10 cm layer of two areas in a 100 m square grid marked with a DGPS. One of the areas is located in Campos Novos Paulista county, SP, Brazil (22 º36 ' 11 " latitude and 50 º00 ' 09 " longitude) on a sandy loam Oxisol. The other area is in Angatuba county, SP, Brazil (23 º29 ' 23 " latitude and 48 º24 ' 46 " longitude) on a clayey Oxisol. Multiple linear regression analysis was carried out for the mean weighted diameter (MWD) results and soil attributes according to the pre-treatments methods (water, alcohol and benzene) and aggregation agents. The results showed that the organic matter content, bacterial community, iron, potassium, and clay content were the most important parameters for soil aggregation. In areas with low clay and high fine sand content it was found low stability indexes. Even though the sandy loam Oxisol has been under no-tillage for over four years, it presented low stability indexes, mainly because of the low clay and high fine sand content. The clayey Oxisol showed higher aggregate stability compared to the sandy loam Oxisol, mainly because of its higher clay and organic matter content.
soil tillage systems; soil physics; soil fertility; soil biology; pre-treatment
