棉田黄顶菊的经济阈值及竞争临界期

黄顶菊是近年在我国发现的外来入侵植物,在河北省已进入农田.为明确黄项菊在棉田中的经济危害允许水平、经济阈值以及竞争临界期,采用添加系列试验和模型拟合的方法,在田间条件下研究黄顶菊不同密度对棉花的生长性状及产量的影响.结果表明,在黄顶菊的竞争干扰下,棉花的叶面积指数、田间透光率、水分利用效率、氮素利用效率和棉花产量均随黄顶菊密度的增加而逐渐降低.当黄顶菊密度为5株/m~2时,叶面积指数、田间透光率、水分利用效率和氮素利用效率显著低于无黄顸菊对照;当密度为2株/m~2时,棉花产量显著低于无黄顶菊对照.对数函数模型可以较好地拟合黄顶菊密度与棉花产量损失间的关系(γ=22.79 lnx十9.0277,R=0.9759).棉田中黄顶菊的经济危害允许水平为0.66%～3.06%,经济阈值为0.69～0.77株/m~2,与棉花的竞争临界期为棉花播种后5.15～83.13天.

Economic threshold and critical period of competition of Flaveria bidentis

Flaveria bidentis (L.) Kuntze was a kind of aggressive alien plant which had invaded farmland in Hebei Province, China. To determine the economic infestation level and economic threshold of F.bidentis in the cotton fields and its critical period of competition, additive series experiment and curve fit were adopted to study the changes of yield characters of cotton under different densities of F.bidentis in the fields. The results showed that with the interference of F.bidentis, the leaf area index, light penetration rate, water use efficiency, utilization rate of nitrogen and output of cotton decreased gradually as the weed density increased. The leaf area index, light penetration rate, water use efficiency and utilization rate of nitrogen of cotton was significantly lower than those of control when the density of F.bidentis was 5 plants per m² and the cotton yield was significantly lower than that of control when the density of F.bidentis was 2 plants per m². The logarithmic regression model was relatively better in describing the relationship between F.bidentis density and yield loss of cotton (y=22.79 lnx+9.0277, R=0.9759). The economic infestation level for F.bidentis in cotton fields was between the range of 0.66% and 3.06%, the economic threshold was 0.69-0.77 plants per m², the critical period of competition was 5.15-83.13 d after cotton sowing.