Objective  To understand the effect of hydroponic tillage time on the soil properties of paddy fields in the subtropical low hills.

  Method  two geomorphic units of valley side and hills in the Jinqu basin of Zhejiang Province were selected for observing the morphological characteristics of Stagnic Anthrosols developed from quaternary red clay with different hydroponic cultivation times. While genetic horizon samples of the soils were collected to characterize the soil physical and chemical properties.

  Result  The results showed that the soil color changed from red to yellow, and the hue changed from 2.5YR to 7.5YR or 10YR with the increase of hydraulic tillage time. As hydraulic tillage time increase, the clay contents in the surface soil decreased gradually, the accumulation of organic matter, total phosphorus and available phosphorus, pH, CEC and active iron gradually increased, and the soil free iron oxide gradually moved down and accumulated in the subsurface soil. With increasing time, the influence of hydroponic tillage time on soil properties developed from surface layer to subsurface layer.

  Conclusion  The results showed that the effect of hydroponic time on soil properties of paddy field on valley side was greater than those on hills due to different water conditions. It took about 15 years to form the typical Stagnic Anthrosols and more than 150 years to form Fe-accumuli-Stagnic Anthrosols by transforming upland of the quaternary red clay into paddy field. When the hydroponic cultivation time was less than 150 years, the Hapli-Stagnic Anthrosols was generally formed. The results also showed that with the increase of rice planting time, the proportion of active organic matter in total organic matter increased simultaneously with the accumulation of total organic matter, and the subsurface soil of Stagnic Anthrosols had strong carbon fixation potential.