抄録
1. Lodging of rice plant affected by drainage or deep water irrigation practice at different time was studied (Table 1). Soil moisture, Eh-6 of soil and NH4-N content of the soil layer of 5∼6 cm depth are influenced by drainage (Fig. 1). Drainage or deep water irrigation produces the good or adverse effect on breaking strength of the internodes N4 and N3 of var. Norin No. 8, which are elongating just at that time, but scarcely affects on the internodes of var. Yuubae, which elongate after that time (Fig. 2). And index of lodging corresponds nearly with the natural lodging of rice plant in the field (Table 2). The development of lysigenous aerenchyma and the mechanical tissue of the internode N3 is makedly affected by tratment. 2. Progressive change of the index of lodging at ripening stage was studied. Breaking strength of the lower internodes becomes small rapidly during 30 days after heading time, nevertheless moment varies in small scale. So, when the index of lodging (distance of fulcra is 5 cm) rises above 200, the plant is liable to lodge (Fig. 3).
