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Farmers are increasingly planting vegetables during the winter fallow period in the double-rice growing area of Guangdong Province, southern China. The intensified winter crop rotation system (rice-rice-vegetable, RRV) may improve the annual planting benefit and change the soil fertility. To address this, yields, biomass, and profitability of each crop in the RRV, relative to the traditional rice-rice-fallow system (RRF), were compared, and the dynamics of physical, chemical and biological properties of soil at different crop stages were determined in this paper. The annual crop yield, biomass and economic return of RRV were significantly higher than those of RRF due to the inclusion of winter vegetables (green beans) in the cropping system. The contribution of green beans to the total revenue per year for RRV was as high as 73%. Filling winter fallow with green beans had no influence on the yield of early and late rice. Soil NO 3 −-N, available P, exchangeable K, exchangeable Fe, exchangeable Cu and acid phosphatase activity at the winter stage were significantly higher in RRV than in RRF, whereas soil pH, soil organic carbon (SOC), dissolved organic carbon (DOC), exchangeable Ca, exchangeable Mg, catalase activity, dehydrogenase activity and invertase activity at the winter stage were lower. The soil NO 3 −-N, exchangeable Fe, exchangeable Cu, and acid phosphatase activity during the early rice stage also tended to be higher in the RRV system. The annual dynamics of soil physical, chemical and biological properties were proven to be greater in the RRV system than in the RRF system. The findings of our study contribute to the understanding of dynamic changes in physical, chemical and biological properties of soil across different crop stages due to intensified green bean planting during the winter fallow period in a double-rice cropping system, which will be useful for the sustainable development of RRV. • Yield and economic income increased significantly in RRV system than RRF system. • Most soil nutrients content were significantly higher in RRV than in RRF. • Soil pH, SOC, and some soil enzyme activity were lower in RRV than in RRF. • The annual dynamics of soil properties were proved to be greater in RRV than in RRF. [ABSTRACT FROM AUTHOR]

• BBU could harvest similar grain yield of rice with FP treatment. • N releasing rate of CRU was higher during late rice season than early rice season. • N release rate of S-CRU were slower and less sensitive to temperature than P-CRU. • S-BBU was more close to the N requirement of rice than P-BBU. Single basal application of bulk blending urea(BBU) which consists of both controlled-released urea(CRU) and conventional urea(U) has been proposed to facilitate fertilization and lower cost of CRU. Nevertheless, its effect on the growth, yield and N use efficiency(NUE) of rice in double rice cropping system under subtropical environment are still unknown. Field experiments were conducted at two different sites(Taishan county and Wengyuan county) simultaneously in Guangdong province to investigate the effects of single basal application of two types of BBU(P-BBU which consists of parabolic pattern CRU, and S-BBU which consists of sigmodial pattern CRU) on soil available N, grain yield and NUE. Conventional high-yield fertilization treatment with four split applications of U(FP) and no-N treatment(CK) were established as controls. The results demonstrated that BBU could provide similar or more adequate N nutrient for rice with FP during late rice season. BBU performed comparably to or better than FP on soil NH 4 +-N, dry matter, grain yield and NUE during late rice season. During early rice season, BBU performed comparably with FP on soil NH 4 +-N, N content of rice, dry matter, grain yield and NUE at Taishan site, while at Wengyuan site, it significantly reduced soil NH 4 +-N, N content of rice, dry matter and NUE compared with FP, and reduced grain yield slightly. Release tests in water and paddy field were conducted in order to evaluate the releasing dynamics of parabolic and sigmodial pattern CRU. Results showed that the N release rate of CRU in paddy field during early rice season was significantly slower than that during late rice season. This was closely correlated with the changing pattern of accumulated temperature. The N release rate of parabolic CRU in paddy field was faster and more sensitive to changing temperature than sigmodial CRU. Non-linear regression analysis shows that the N release patterns of sigmodial CRU in paddy fields were more close to N uptake of rice during both rice seasons. The grain yield of rice and NUE in S-BBU was higher slightly than P-BBU during both rice seasons. These results demonstrated that BBU obtained similar grain yield in double rice cropping system in South China, and S-BBU treatment is better for N requirement of rice during both seasons. Future studies should focus on optimizing and customizing the blending ratio of BBU for each rice season in double rice cropping system to increase crop yield and the robustness of BBU to changing weather conditions. [ABSTRACT FROM AUTHOR]