Fewer hills with more seedlings improved lodging resistance of whole hill and yield stability of machine-transplanted rice

Lodging is a leading cause of yield loss in rice (Oryza sativa L.). To elucidate the effect of field configuration on lodging-related traits at the single-stem and whole hill levels, indica hybrid rice cultivars, Yixiangyou2115 and Shuyou217, were grown under traditional dense planting (30 x 12 cm row-hill spacing) and under fewer hills with more seedlings (30 x 23 cm row-hill spacing) in 2019 and 2020. The results show that there was no significant difference in single-stem lodging index between fewer hills with more seedlings and traditional dense planting, as shown by the similarity in plant height, relative gravity center height, culm wall thickness, culm diameter, and breaking strength. However, compared with traditional dense planting, fewer hills with more seedlings significantly increased the anti-thrust of whole plant and the ventilation rate between whole hills by 45.02%-117.36% and 58.18%-117.39%, respectively. This contributed to the marked improvement in the lodging resistance of whole rice hills, where plant inclination angle and apparent lodging rate were reduced by 41.75%-75.46% and 53.49%-63.33%, respectively. Furthermore, there was no significant difference in grain yield between the two configurations. These results indicate that the field configuration of fewer hills with more seedlings can improve the lodging resistance of whole hills while maintaining the grain yield of machine-transplanted rice.