我国南方晚稻孕穗期旱灾指标试验研究

根据我国南方晚稻孕穗普遍期后对干旱最敏感这一特点,分别在江西南昌、湖北荆州、湖南长沙3个试验站设计了孕穗普遍期后7d、10d、13d、16d和直至植株死亡5种干旱天数。试验结果表明:干旱天数与穗粒数、穗结实粒数呈负相关,相关系数分别为-0.956和-0.959。随着干旱天数增加,土壤湿度逐渐减少,减产率上升。当干旱18d时,土壤湿度临界值为5.57%,植株死亡。用线性和非线性回归拟合干旱天数、土壤湿度、减产率三者之间的方程,分别以土壤湿度、减产率作为评价因子得出干旱灾害评价标准。经鉴定,自大田土壤上层无水开始干旱6～7d,晚稻受到轻度灾害;干旱8～11d,晚稻受中度灾害;干旱12d以上受重度灾害。

Tests on Droughts Indexes for Late Rice in Southern China

According to the fact that late rice responses to droughts most sensitively after booting stage,five drought indexes are designed in the tests：the numbers of drought days after booting stage being 7,10,13,16 days and till plant death,respectively.The results show that there exist significant negative correlations between the number of drought days and the number of grains per spike,the number of filled grains per spike.The correlation coefficients are-0.956 and-0.959.Soil moisture decreases rapidly and yield reduction rate rises with the increasing number of drought days.When the number of drought days is up to 18,the plants go dead at a critical soil moisture of 5.57%.The linear and nonlinear regression methods are applied in establishing the equations among the number of drought days,soil moisture,and yield reduction rate.It is concluded that there is slight influence in the first 6 to 7 days of droughts,moderate influence in 8 to 11 days,severe influence over 12 days.