Abstract: While rice bunch mingled with transplanted barnyardgrass(TB), the tillering rate of TB is faster than rice. The highest increasing rate of tiller number are 1260% and 680% respectively for TB and rice. The height of TB is 40-50 cm higher than that of rice. Meanwhile, higher leaf area index, longer root and larger absorbed area of root surface accompany with TB comparing to rice. Which means the growth potential of TB is stronger than rice. The dry matter ratios of barnyardgrass to rice are located between 1.6 and 2.5 from mid-tillering stage to heading stage. The experiment of different rates of rice bunch mingled with TB showed, tiller number and yield of rice decrease significantly as the rate of rice bunch mingled with TB increases. About 50% tillers and more than 50% yield are reduced when rate of rice bunch mingled with TB is 100% compared to CK (without TB). Using rate of rice bunch mingled with TB as independent variables(x), and decreasing rate of rice effective panicle number and rice yield as dependent variables (y₁) and (y₂), the regression equations were as following:for Weiyou 4, y₁ =1.41 [52.05/(52.05+x)]x, y₂= 1.46[57.07/(57. 07+x)]x; for Xiangzaokian 7, y₁=0. 87[83. 83/(83. 83+x)]x, y₂= 2.61 [27.51/(27. 51+x)]x.

Key words: competitive growth, correlated equation, rice, transplanted barnyardgrass

摘要： 稻蔸夹稗时，夹蔸稗分蘖生长势远远强于水稻，其最高分蘖增长率夹蔸稗和水稻分别为1260%和680%；夹蔸稗的株高一般高于水稻40-50 cm，覆盖在水稻的顶层，叶面积指数及根长和根表吸收面积亦大于水稻，因此，夹蔸稗的生长势总是超过水稻。水稻分蘖盛期到抽穗期内稗／稻干物质比在1.6～2.5之间。水稻不同夹稗蔸率试验结果表明，随着夹稗蔸率的提高，分蘖数显著减少，减产幅度加大。当夹稗蔸率为100%时，分蘖数比对照减少50%左右，减产50%以上。以水稻夹稗蔸率百分数为自变量（x），以水稻有效穗减少百分率（y₁）或稻谷减产百分率（y₂）为依变量，它们之间的关系均符合曲线方程y=m[k/(k+x)]x(m、k为待定参数）。

关键词: 竞争生长, 相关方程, 水稻, 夹蔸稗