Effect of various crops rotations on soil quality in double cropping rice field in the middle reaches of the Yangtze River

Improved knowledge that may support the efficient utilization and sustainable development of agricultural resources in the middle reaches of the Yangtze River is still needed. Herein, changes on soil nutrients, organic carbon, and enzyme activities under different planting patterns and straw retention were assessed, and the impact of agricultural management measures on soil quality was evaluated in this particular geographical region. The long-term positioning experiment of different rotational and continuous cropping was carried out from 2012 to 2017, and five treatments of rotation patterns including winter fallow-early rice-late rice, winter Chinese milk vetch-early rice-late rice, winter oilseed rape-early rice-late rice, winter garlic-early rice-late rice, and winter rotation (interannual rotation of potato, Chinese milk vetch, oilseed rape, and garlic)-early rice-late rice were set up. Under the condition of winter crop straw and rice straw retention, the soil quality indexes in minimum data set were selected and determined using multiple variance analysis, correlation analysis, and principal component analysis combined with the suitability of the soil in the southern double cropping rice field. Lastly, the fuzzy mathematics method was used to evaluate the soil quality in the double cropping rice area. The data indicated that six years of winter planting suitable crops and straw retention in the double cropping rice area could effectively improve the soil quality of paddy field by 10.73%-12.91% compared with the winter fallow treatment, with exception of the garlic treatment. The soil quality of double cropping rice field under different rotation patterns was in the order of winter rotation (planting different crops in different years during winter) (0.726) > planting oilseed rape in winter (0.723) > planting Chinese milk vetch in winter (0.712) > winter fallow (0.643) > planting garlic in winter (0.638). Therefore, the soil quality of double cropping rice can be significantly improved by suitable rotation with winter crops and double straw returning, which provides a solid foundation for the healthy and sustainable development of paddy fields in southern China.