1. The heavily fertilized rice plant is easier to lodge by breaking of culm than the plant applied with usual dose of fertilizers. The former plant is different from the latter in size and character as follows ; the plant is high, the weight of plant is heavy, the lower internodes (N
4 and N
3) are long and slender, the thickness of culm wall is thin, the weight of unit length of culm is small, the development of the mechanical tissue of culm is inferior and the breaking strength of N
4 or N
8 is small. The moment (plant height x weight of plant) of the upper part of the internode concerned is large. Accordingly, the ratio of moment to breaking strength of the internode concerned (index of lodging) is large, and the plant is liable to lodge (Fig. 1). 2. Index of lodging of N
4 and N
3 of the rice plant, which is supplied with chemical fertilizers, is larger than that of the plant of the plant grown with compost, so the former plant is liable to lodge (Fig. 2). 3. Shading the late variety Aichi-asahi (heading date is Sept. 6) during the first decade of Aug. accelerates the elongation of the internode N
4, which is elongating just at that time, but retards the enrichment of N
4. Consequently, breaking strength of N
4 is small, index of lodging is large, so that the plant is liable to lodge (Fig. 3). 4. Top-dressing of plenty of ammonium sulphate at about 40 days before heading time makes plant liable to lodge, because index of lodging or N
4 or N
8 becomes large (Fig. 4).
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