Abstract : Conservation tillage practices are increasingly being used by the farmers; however, their impacts on soil physical properties remain poorly documented, especially when they are combined to manure fertilization. This study aimed at evaluating the effect of reduced tillage and manure fertilization on soil structure and its permeability, particularly in relation with earthworm activity. This study was conducted at the Kerguéhennec experimental station, established in 2000, located in Brittany, France. Three tillage treatments were compared (moldboard plowing, surface tillage and no-tillage) along with two types of fertilizers (poultry manure and mineral). In the first part of this work, we were interested on methodologies to quantify earthworm biostructures (burrows and casts) and the impact of cultural practices on their abundance. In a second part, we have measured the combined effect of cultural practices and earthworm biostructures on the structural stability of aggregates, macroporosity and permeability of soil during one growing season. This work demonstrates the difficulty of quantify earthworm biostructures, particularly earthworm casts. We proposed various indicators, that, when combined provide a good estimate of the abundance of casts. Our results confirm that the abundance of biostructures increases under no-tillage and with manure fertilisation. We also showed that these biostructures evolved during the crop year as a result of climate, tillage and probably the physiological activity of earthworms. Tillage practices alone had a strong impact on soil physical properties in comparison to manure fertilization. Reduced tillage increased soil aggregate stability: this increase was not explained by earthworm activity. No tillage had the lowest soil macroporosity and permeability but the earthworm activity was highest in that treatment. Soil physical properties have changed during the cropping year. The dynamics of soil aggregate stability was affected by the climate with similar fashion in all treatments. Earthworm activity, tillage events and climate were linked closely to the dynamics of soil permeability under tilled treatments. Theses factors influence mainly one class of porosity, the inter-aggregate complex macropores. Under no-tillage, the dynamics of soil permeability was affected by the climate and the abundance of earthworm casts, without significant modification of soil macroporosity (size and shape). Thus, in the experimental conditions of this work, the surface tillage practice has reflected the best soil physical properties, while manure fertilization does not show any obvious impact on the studied soil physical properties. Moreover, our study highlights the importance of earthworm casts on the short term soil permeability variations.