RICE RATOONING - IRRI books - International Rice Research Institute

Some factors influencingthe growth of rice ratoonM. lchiiKagawa UniversityKagawa, JapanABSTRACTRatoon growth varies according to the internal and external environments of thestubble. The effects of temperature, soil fertility, and reserves of the main crop stubblewere determined.Grain yield and the other agronomic characters in the rice ratoon crop differsignificantly among cultivars (1, 6, 7). Ratoon growth, however, may vary accordingto internal and external factors affecting the stubble. These factors includetemperature, soil fertility, and reserves contained in the stubble. This paper presentsthe effects of these factors on ratoon growth.TEMPERATUREHigh temperature causes vigorous ratoon growth. The higher the temperature, themore tillers are formed, the higher their rate of increase, and the higher the foliageweight of the ratoon plant. Tiller number varied with temperature and reached themaximum 5-10 d after main crop harvest (Fig. 1).Over 20 d, ratoon plant foliage weight increased linearly and stem base weightdecreased. In sunlight and at higher temperature, foliage weight increasedexponentially and stem base weight decreased linearly. In darkness, foliage weightand stem base weight decreased linearly. These facts indicate that ratoon growth isactivated by photosynthesis of ratoon foliage. Moreover, it is inferred thatsubstances in the stem base play an important role in the growth and respiration ofthe ratoon plant.Figure 2 shows changes in the sum of stem base weight and foliage weight ofthe ratoon plant for 20 d. The sums remained almost constant for the first 10 d, thenfoliage weight and stem base weight of the ratoon plants in the high-temperature,sunlit environment increased significantly. This suggested that ratoon foliagecontributed its photosynthetic products to its own growth. That the sums in darkenvironments were almost constant throughout the period suggested that substancesin the stem base were consumed for respiration.