关键词: 双季稻, 秸秆还田, 轮耕, 土壤容重, 团聚体稳定性, 土壤碳氮

Abstract: In order to explore the effects of straw returning and rotating tillage on soil physical properties，carbon and nitrogen in double‐cropping rice area，we set four different tillage modes，including rotary tillage for early rice and turning tillage for late rice with straw returning（RTS），rotary tillage for early rice and no tillage for late rice with straw returning（RNS），rotary tillage for early rice and turning tillage for late rice without straw returning（RT），rotary tillage for early rice and no tillage for late rice without straw returning（RN）in Liuyang City，Hunan Province. The results showed that the particle size distribution and carbon and nitrogen contribution rate of soil aggregates were dominated by 0.25—2 mm in each treatment. Soil bulk density under no‐tillage for late rice was higher than that under rotation tillage for early rice，the rotary tillage of early rice reduced the soil bulk density of no-tillage late rice last year.Compared with no straw returning，straw returning increased the stability of soil aggregates（0—20 cm soil layer），and the concentration of large aggregates（>0. 25 mm），mean weight diameter（MWD），soil organic carbon（SOC），total nitrogen（TN）were increased by 2.49%—12.72%，1.23%—12.34%，8.46%—36.70%，8.96%—81.25%，respectively.After using different tillage methods for late rice，the concentration of >0. 25 mm aggregates was significantly increased. And no tillage could improve the aggregate concentration（>0.25 mm）more than that of turning tillage in 10—20 cm soil layer.Compared with other treatments，the concentration of large aggregates and organic carbon content in 0—20 cm soil layer under RNS increased by 1.87%—21.67% and 5.76%—19.36%，respectively. Therefore，RNS is helpful to maintain soil aggregate stability and increase soil organic carbon content.

Key words: Double‐cropping rice, Straw returning to field, Rotating tillage, Soil bulk density, Aggregate stability, Soil carbon and nitrogen