Abstract:

In Hubei plain area, there is intensive rainfall in summer. During this season, rice field is liable to suffer from flooding disaster. In order to find out the influence of flooding on growth of hybrid rice and put forward relative drainage index, flooding depth and flooding duration representing  different flooding stresses were individually simulated in the booting and tillering stages of hybrid rice. The results show that after flooding treatment, rice height, the 3th and 4th internode length all presented elongation. Significant linear positive relationships of these three indexes were also found with the accumulated value of flooding depth and duration time (SD). However, the rice height was found to be shorter than the control when harvested, and the heavier the flooding degree was, the shorter the rice height was at harvest. Flooding was the cause of rice yield loss, longer flood duration and deeper flood depth caused more serious rice yield loss. Using the yield as an appraisal index, flooding stress in booting stage was more sensitive than in tillering stage. As far as yield component is concerned, flooding stress in tillering stage lead to yield loss mainly in the following aspects. Firstly, the decline in effective ears followed by the decrease in seeds setting percentage; while in the booting stage 1000grain weight and seed setting rate decreased followed by the decline in effective ears. The regression equation for the parameters of elative yield (Ry) dramatically showed the relationship between Ry and SD, Ry and the flooding depth, flooding duration, which can be used as rice drainage equation in tillering and booting stage. As for the flooding components, flooding depth had a greater influence on the yield than flooding duration in tillering stage; while in booting stage flooding depth and duraiton had the same effect on yield.If the rice yield decreased by 20%-30% as the drainage flooding standard, the corresponding values of SD was 1106-1944 cm/d in tillering stage(flooding depth≥18 cm) and 265-805 cm/d in booting stage(flooding depth≥25 cm). The exact drainage days about the concrete flooding depth was put forward as well