In this study, the reaction force of a rice stalk undergoing forced displacement was analysed based on a mechanical model of a crop stalk. Horizontal and vertical reaction forces of a single rice stalk undergoing forced displacement were measured. The horizontal force increased linearly for small curvatures of the rice stalk; after that, force increments decreased with displacement due to large curvature of the stalk. The vertical reaction force had different tendencies, depending on the initial shape of the rice stalk. The main reason for the differences was a directional change in friction, depending on the initial shape. An intrinsic shape function of a rice stalk was proposed. An equation of curvature describing rice stalk bending was derived by considering the curvature due to intrinsic shape, and used for analysis of the reaction force. The analytical results coincided fairly well with measured values, and it was demonstrated that the reaction forces of a single rice stalk according to the initial shape was accurately predicted by numerical calculation.
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