Appropriate Time of Deep-Water Treatment for Regulation of Rice Growth(Agronomy)

Abstract

In Japan, deep-water treatment is occasionally used to regulate the rice growth. For practical use of this method, it is necessary to determine the appropriate time of treatment. In this study, deep-water treatment (water depth level: 3cm above the auricle of the fully expanded leaf) was given for 16 days from the start of the tillering stage (DW A), from the end of the early tillering stage (DW B), from the active tillering stage (DW C) or from just prior to the maximum tiller-number stage (DW D). The percentage productive culms was high in the DW C plot (26 points higher than the control plot), while it was low in DW A, B and D plots. In the DW C plot, not only the panicle number, but also the weight and length of panicles were increased. In the DW B, C and D plots, the diameter of the basal two internodes, which are closely related to lodging, was larger than that in the control plot, but the breaking strength of internodes was not increased. In the DW D plot, although the diameter of the basal two internodes increased by 20% as compared with the control, the breaking strength was reduced by 20∼24% due to the well-developed aerenchyma within the parenchyma. Thus, the deep-water treatment from the active tillering stage to the maximum tiller-number stage was effective for improving rice growth. However, an earlier treatment was less effective, and a later treatment was suggested to reduce the lodging resistance due to the well-developed aerenchyma in the internodes.