Changes of Cropping System and Suggestions on Ecological Cultivation Regions of Soybeans in China

The soybean cropping system involves its distribution across the country, the lighting time, accumulated temperature and cropping system of the varieties, the rotation system, as well as the monocropping, intercropping and relay intercropping methods, serves as the foundation for soybean production, breeding, introduction, and technology innovation. Optimizing the soybean cropping system is of decisive significance for enhancing the comprehensive production capacity and benefits of soybeans in China. Since the founding of the People's Republic of China (PRC) 70 years ago, the area planted with soybeans in regions with one crop per year system has expanded, while the area in regions that have shifted from triple crops per two years system to double crops per year system has decreased. In areas that have transitioned from double crops per year and then to triple crops per year, the area planted with soybeans has remained stable with a slight increase. From a national perspective, the soybean cultivation region has expanded to the northern part of Northeast China, and the soybean cultivation region in the South and Southwest has remained stable with a slight increase. The Northwest region has performed a new high-yield area for soybeans. Historically, the division of soybean cultivation regions was based on the basic data, investigations and experiments of the planting system at that time. In the recent 30 years, there have been significant advancements in soybean production, breeding and cultivation techniques, especially in the changes of soybean cultivation areas. The division of ecological cultivation region is a fundamental task closely related to soybean cultivation, resource utilization, introduction and breeding for cultivars. Based on the review of the changes in soybean cultivation region in China since the PRC establishment, including the northward expansion and southward shift of cultivation region, the renewal and upgrading of varieties, the improvement of mechanization levels, the comprehensive progress of cultivation techniques, and the promotion of intercropping system, especially the emphasis on developing the soybean industry as a national policy in China since 2000, this review comprehensively analyzed the dynamic characteristics of the soybean cropping system and technical system in PRC and thus proposed suggestions for adjusting the ecological cultivation region divisions of soybeans. From which a new soybean ecological cultivation region system is proposed. The main results comprise the changes in soybean cropping regions and the advances in cropping system, the environmental cultivation regions and changes of soybeans, the ecology of modern soybeans in China, and discussion and prospect on ecological cultivation region of soybeans in China. Influenced by updates of soybean cultivars, advancements in cultivation and farming technology, and requirements on food security, the soybean cropping system has undergone significant changes. The new six ecological cultivation regions were suggested as Northeast Spring Planting Soybean Ecological Cultivation Region, Northwest Spring Planting Soybean Ecological Cultivation Region, Huang-Huai-Hai Summer Planting Soybean Ecological Cultivation Region, Changjiang Valleys Spring-Summer-Autumn Planting Soybean Ecological Cultivation Region, Southwest Plateau Spring-Summer Planting Soybean Ecological Cultivation Region, and South China All Season Planting Soybean Ecological Cultivation Region. This division and naming system is considered as consistent as that of the national crop cultivation system, and also pays attention to the connection with previous ecological cultivation region division systems in soybean.