Abstract: In this study, six model demonstration sites of rice-crayfish coculture (CR) and rice monocropping (MR, as control) in Yangzhou were selected to analyze the content of soil reducing substances, total nutrients and available nutrients across different planting years (1, 2, 3 years), soil layers (0-20, 20-40, 40-60 cm), and the growth period of rice (tillering stage, jointing booting stage, maturity stage), aiming to reveal the temporal and spatial variations of soil physicochemical properties of rice-crayfish coculture and to provide theoretical reference for field management and sustainable development of this model. The results showed that with the increases of planting years, CR increased the  active reducing substances, Mn²⁺ and Fe²⁺ contents  in 0-40 cm soil layer than MR, and such differences increased annually. The active reducing substances in 0-20 cm soil layer of CR was significantly higher than that of MR (P<0.05).The proportion of soil available phosphorus in 0-20 cm soil layer increased significantly under CR after operated for 2 to 3 years, compared with that for 1 year (P<0.05). There was no significant difference in ammonium nitrogen, available nitrogen, available nitrogen proportion, and available phosphorus over time among different treatments, but CR had a certain increasing trend compared with MR (P>0.05). In conclusion, CR could improve nitrogen and phosphorus availability in surface soil (0-20 cm) and thus soil fertility, but increase the risk of secondary gleyization in 0-40 cm soil layer compared with MR.

Key words: rice-crayfish cultivation mode, reducing compound, secondary gleyization, nutrient supply capacity.