Abstract: To clarify the effects of organic rice-duck farming on soil physicochemical properties and bacterial community in different depths of tillage layer, field experiments were conducted under three depths of tillage layer (0-6, 6-13 and 13-20 cm) in organic rice-duck farming (ORDF, 12 years) and transition rice-duck farming (TRDF, 3 years) fields. The results showed that after long-term organic rice-duck farming, soil physicochemical properties of 0-6 and 6-13 cm layers was improved to a large extent, but that in 13-20 cm layer changed slightly. Compared with the transitional rice-duck farming, long-term organic riceduck farming significantly changed the bacterial community composition, resulting in a higher proportion of common bacteria in different ploughed soils. Meanwhile, it also improved the richness and diversity of bacterial community and reduced the difference of bacterial community structure in different depths of tillage layer. This was especially evident in 0-6 cm soil layer, which made the structure of bacterial community more stable. Results of correlation analysis showed that pH, soil bulk density, total nitrogen and nitrate concentration were important factors affecting the spatial distribution of soil bacterial community after long-term organic rice-duck farming. In conclusion, long-term organic rice-duck farming affects the spatial distribution of bacterial community mainly by changing soil properties. Therefore, it is an important model to promote the sustainable development of agriculture.

Key words: physio-logical and biochemical characteristic, apple seedling, photosynthesis, rhizosphere-promoting bacteria, drought stress