Abstract
This study aimed to evaluate the relationship between the physicochemical properties and lodging index of different stem internodes and the yield of direct-seeded rice. Two treatments of wheat straw returning (returning and non-returning) and five potassium application rates of 0, 62.5, 125, 187.5, and 250 kg ha-1 were applied. Wheat straw returning combined with a potassium application rate of 125 kg ha-1 significantly promoted potassium accumulation, increased total soluble sugar and lignin contents, improved breaking moment, reduced the flattening rate and lodging resistance index of different internode stems, and increased the yield. Correlation analysis revealed that compared with those of the 4th and 5th internodes, potassium content and accumulation and total soluble sugar and lignin contents of the 3rd internode were significantly positively correlated with yield (r = 0.85**-0.93**) and negatively correlated with the stem flat rate and lodging index (r =-0.67*--0.79**), which improved lodging resistance in collaboration with the 4th and 5th internodes (r = 0.82**-0.95**). Increasing potassium accumulation, total soluble sugar and lignin content, and reducing stem flatness of the 3rd stem internodes are important factors for improving lodg-ing resistance of direct-seeded rice and may provide a basis for improving the 4th and 5th stem internodes.