以6个抗倒伏性有一定差异的中籼稻品种为材料，设置了3个氮肥水平、3个栽插密度，分别测定了各处理下的茎秆力学特性，分析了氮肥用量和栽插密度对水稻茎秆力学特性的影响。结果表明：在同等密度下，随着施氮量的增加，弯曲应力，株高，基节弯矩，都逐渐增大；而倒伏指数先降低再升高，即中肥区倒伏指数最小，倒伏的可能性最小。在同一施氮水平下，随着栽插密度的减小，基节弯矩，断面模数和倒伏指数先减小后增大，弯曲应力先增大后减小，而折断弯矩却明显增高。即在适宜的施肥水平下，栽插不宜过稀也不宜过密。高肥水平下稀植，低肥水平下密植，都有可能降低倒伏指数。稀植条件下，基节折断弯矩的变化单靠构成茎秆材料的数量来实现；密植条件下，基节折断弯矩的变化是通过断面模数和弯曲应力两因素共同实现的。实际生产中，施氮量既不能过高，也不能过低，而且不同类型的品种，对施氮量和栽插密度的要求有所不同。改进现有高产品种茎秆的质地可能是进一步提高水稻抗倒性的有效途径。

The mechanic characteristics of 6 varieties with different lodging-resistance at 3 nitrogen levels and 3 planting densities were determined．The results showed that in the same density, as the amount of nitrogen increased, bending stress, plant height, the basal internode moment are gradually increasing; but the Lodging index reduced at first, and then increased, that is, in middling fertility area, the smallest lodging index ,the least possibility of lodging. At the same level of nitrogen, as the planting density decreased, the basal internode moment, secontion modulus and lodging index increased after the first reduced, bending stress increased and then decreased, while breaking moment has increased significantly. That is, in the appropriate level of fertilization, planting should not be too thin nor too dense. In high fertility area planted thinly and in low fertility area planted densely, which may reduce the lodging index. Sparse conditions, the changes of the basal internode moment only depend on the number of stem materials to be achieved; in dense-planting conditions, the changes of the basal internode breaking moment are through the changes of section modulus and bending stress two factors together to be acheieved. In the actual production, the amount of nitrogen can neither too high nor too low, further more, different types of species, require different volume of nitrogen and planting density. The improvement of the quality stem of existing high-yield varieties may be an effective means of further improved lodging -resistance of rice.