Abstract:To compare the effects of different soil tillage methods (ploughing, rotary tillage and no tillage) on rice yield composition and cadmium accumulation and distribution traits in rice panicles in southern double-cropping rice fields, and to explore the optimal soil tillage method for double-cropping rice in cadmium-contaminated rice fields, taking "Lingliangyou 211"and "Weiyou 46"as early and late rice varieties, the available cadmium content in soil, rice yield components and spike cadmium accumulation and distribution of double-cropping rice under five soil tillage methods (double-cropping no-tillage, double-cropping ploughing, double-cropping rotary tillage, ploughing in early rice and no-tillage in late rice, rotary tillage in early rice and no-tillage in late rice) were studied in Yisuhe Town, Xiangtan County, Hunan Province in 2015 to 2017. The experimental field was cadmium-contaminated rice fields, and the total cadmium content was 0.86 mg/kg. The results showed that the yield of double cropping rice was the highest in the treatment of double-cropping ploughing, followed by the treatments of ploughing in early rice and no-tillage in late rice, double-cropping rotary tillage and rotary tillage in early rice and no-tillage in late rice, and that of no-tillage in double cropping rice was the lowest. The highest yield of ploughing treatment was due to the higher number of effective panicle and grains per panicle. (2) The cadmium content in panicle generally showed an increasing trend from full heading to maturity stage. In the first year of early and late rice, the cadmium content in panicle at full heading stage was the highest in no-tillage treatment, but no-tillage could significantly reduce the growth rate of cadmium content in panicle from full heading to maturity stage. The cadmium content in panicle at maturity stage was higher in ploughing treatment and lower in no-tillage and rotary tillage treatment, there were difference between no-tillage and rotary tillage treatment, but they were different among years and seasons. (3) Cadmium content in different parts of rice panicle at maturity stage followed the order of branches > husks > brown rice. The cadmium content in brown rice was higher in no-tillage treatment in the first year, but in the second and third years, that of no-tillage was lower than that of ploughing and rotary tillage. (4) The cadmium accumulation in panicle of early and late rice was lower in rotary tillage treatment in the first year, but it was lower in no-tillage treatment in the second and third years. (5) Compared with other treatments, double-cropping no-tillage significantly improved the soil available cadmium content, while double-cropping rotary tillage decreased the soil available cadmium content. The three-year locational test showed that soil tillage methods had a significant impact on available cadmium in soil, yield components and cadmium accumulation and distribution in rice panicles of double-cropping rice in cadmium-contaminated paddy field. From the perspective of ensuring the yield of double-cropping rice, reducing cadmium content in rice and saving labor, ploughing in early rice and no-tillage in late rice was the optimal soil tillage method for medium cadmium-contaminated double-cropping rice fields.