The ratoon rice system with high yield and high efficiency in China: Progress, trend of theory and technology

The planting area of ratoon rice in China has expanded in recent years to accommodate the warm temperatures and additional sunshine of the autumn season, greatly improving the yields of rice paddies. China is a global leader in both the research and cultivation of ratoon rice. Along with our 30 consecutive years of research, this review summarizes the research progress of theories and technologies relating to the efficient cultivation of highyield ratoon rice based on the following: (1) Five regions in China were designated based on the thermal energy available for cultivating main crop-ratoon rice: Southwestern, Southern, Southeast, Central, and Eastern. (2) Ratooning ability is affected by both genetics and environmental factors. Rice cultivars with strong ratooning ability are characterized by strong root activity and high dry matter weight per stem. (3) Mechanisms underlying the death and yield formation of ratooning buds of rice cultivars with strong ratooning ability were analyzed, and the effects of promoting-bud fertilizers, stubble height, timely harvest of main rice crop, and plant growth regulator on improving the ratooning ability of rice cultivars were examined. (4) An efficient method for applying promoting-bud nitrogen fertilizer has been established based on spikelet number per panicle, chlorophyll content, and target yield of ratoon rice. (5) The large-scale production of ratoon rice has several constraints, such as low and unstable grain yield of ratoon crops, large differences in grain yield between the demonstration area and the expansion area, large-scale destruction of stubble after mechanical harvesting of the main crop, and the need for more land between planting ratoon rice and planting double-season rice. (6) Technologies relating to future development trends in ratoon rice are clarified, including high-quality and labor-saving technologies, high nitrogen and potassium use efficiency technologies, the integration of agricultural machinery and agronomical measures, technological advancements related to the cultivation of ratoon rice, and the optimal economic threshold of rice yield in ratoon rice production.