Physical Traits Related To Rice Lodging Resistance Under Different Simplified-Cultivation Methods

Lodging has been a limiting factor for the achievement of high grain yield and quality in rice (Oryza sativa L.) production. It is necessary to evaluate rice lodging resistance under simplified-cultivation methods widely adopted in China. With this objective, we investigated rice lodging resistance under mechanical transplantation (MT), dry direct-sowing (DDS), and wet direct-sowing (WDS) methods by measuring physical traits of stems. Our results show that, among the three cultivation methods, rice lodging resistance under MT was the strongest while it was the weakest under WDS. The average breaking stress of the two bottom internodes (N-3 and N-4) under MT was 27.11 and 54.65% higher than under DDS and WDS. However, the average lodging index of the two bottom internodes was decreased by 16.08 and 24.69% under MT compared to that under DDS and WDS. These significant differences in lodging resistance were attributed primarily to the changes in physical parameters (i.e., the internode length, internode width, culm wall thickness, dry weight per centimeter of culm and bending moment) of the third and fourth internodes from the top. The rice yield under WDS only reached 5.08Mg ha(-1), which was 45.68 and 36.89% lower than that under MT and DDS. The results suggest that this severe damage to grain yield was due to lodging occurrence. Therefore, it is urgent to apply agronomic management practices to mitigate sustainably the risk of lodging in rice production, particularly for direct-seeded rice.