Abstract: Rice lodging can reduce rice yield and quality, with consequences on the economic benefits of rice production. In order to explore the effects of the combination of biochar and rice-duck co-cultivation on rice stalk and lodging traits, we carried out an experiment with four treatments, including applying biochar with raising ducks in paddy field (CD), applying biochar without raising ducks in paddy field (CR), no biochar with raising ducks in paddy field (D), and no biochar and no ducks in paddy field (R). We analyzed the morphological structure, anatomical structure and mechanical characteristics of rice stalks. The results showed that, compared with the treatment R, the height of the center of gravity and the length of the internodes of rice were reduced, the stem thickness and internode fullness were increased, and the area of vascular bundles was significantly increased under treatments of CD, CR, and D. The increases of the first internode, the second internode, and the third internode were 24.15%-35.91%, 12.75%-62.19%, and 4.66%-73.87%, respectively. The morphology of rice vascular bundles changed, while the bending moment and lodging index of rice internodes decreased. The bending moments of the first internode, the second internode, the third internode and the fourth internode decreased by 24.05%-31.65%, 24.55%-26.27%, 32.28%-37.83%, and 21.79%-32.37%, respectively. The lodging index of the first and the second internodes decreased by 45.69%-52.04% and 38.86%-48.16%, respectively. The bending resistance of rice stalks also increased, with an increase rate of 19.86%-54.02% and 20.62%-39.23% for the first and the second internodes, respectively. The bending resistance was positively correlated with internode fullness and stem thickness, and negatively correlated with length. The lodging index of each internode was significantly negatively correlated with the internode fullness, but positively related to the internode length and bending moment. Therefore, the application of biochar in rice-duck farming system can reduce the height of the center of gravity, increase internode fullness, change vascular bundle morphology, and thus improve lodging resistance of rice.

Key words: rice-duck mutualism, biochar, morphological structure, anatomical structure, lodging.