Progress and challenges of rice ratooning technology in Guangdong Province, China

Mechanized ratoon rice has the advantages of low labor requirement, low costs, and high profit. In 1970s scientists and technicians in Guangdong made intensive efforts on the research and extension of cultivation technique of traditional manual-harvested ratoon rice. Recently substantial progresses in the development of lowstubble mechanized rice ratooning technology have been achieved as follows: (1) Suitable cultivars, such as Meixiangzhan2 and Qingxiangyou132, with high ratooning ability for ratoon rice system have been identified; (2) Studies revealed that the ratooning ability of rice was significantly related to the crop traits at grain-filling stage of main crop such as light transmission ratio, root activity, leaf SPAD value attenuation, and culm and sheath weight stem-1; (3) Fertilizer nitrogen (N) management strategy consisting of the late and light application of budpromoting N and the heavy application of tiller-promoting N and panicle-promoting N has been developed. Reasonable water management method including digging surrounding ditch, draining field twice in main crop, and keeping soil wet during the initiation of axillary buds has been established; and (4) Demonstrations of lowstubble mechanized rice ratooning technology were carried out from 2017 to 2022. The ratoon crop yield ranged from 4.10 to 6.92 t ha1 and increased year by year. Further efforts should be made on screening or breeding more cultivars suitable for mechanized ratoon rice, better understanding of the mechanisms of initiation of axillary buds and growth of regenerated tillers, and developing combine harvesters with less stubble damage. We believe that as the agro-food system transformation strengthens the mechanized rice ratooning will become one of the promising cropping systems in Guangdong as well as in South China.