| Eragrostis japonica（Thunb.）Trin.is a gramineous annual weed,the occurrence in rice fields has increased in recent years.In order to effectively control E.japonica in paddy field,The ability of E.japonica competed with Echinochloa crusgalli（L.）Beauv.and Leptochloa chinensis（L.）Nees.respectively was compared.The effect of weeds on rice yield traits and their eco-economic thresholds were measured when E.japonica alone,E.crusgalli alone and they grew togather.The control effects of 6 herbicides on 14 different populations of E.japonica was were determined.The interaction of between metamifop and fluroxypyr on E.japonica at two leaf-stages was evaluated with the Gowing’s method.The combined effect of propanil,metamifop and fluroxypyr on the control of 6-leaf-stage E.japonica was evaluateed with Colby’s method.The main results were as follows:1.The results of the competition test between E.japonica and E.crusgalli showed that when E.japonica.was as the target plant（TP）,the competition model curve slope of adjacent E.crusgalli→E.japonica（TP）was 0.5682,which is greater than that of adjacent E.japonica→E.japonica（TP,0.2527）,which indicated that E.crusgalli has stronger competitiveness;When E.crusgalli was as the target plant,the competition model curve slope of adjacent E.crusgalli→E.crusgalli（TP）was 0.3074,which is greater than that of adjacent E.japonica→E.crusgalli（TP,0.1516）,which also shows that the competitiveness of E.crusgalli was stronger than E.japonica.In the two-way competition test between E.japonica and L.chinensis,when E.japonica was as the target plant,the competition model curve slope of adjacent L.chinensis→ E.japonica（TP）was 0.4328,which is greater than that of adjacent E.japonica→ E.japonica（TP,0.2527）,which indicated that the competitiveness of L.chinensis was stronger;When L.chinensis was as the target plant,the competition model curve slope of adjacent L.chinensis→L.chinensis（TP）was 0.2389,which was greater than that of adjacent E.japonica→ L.chinensis（TP,0.1462）,which also showed that the competitiveness of L.chinensis was stronger than E.japonica.The effect of weed density on traits of rice yield was tested,The results of showed that the panicle length,number of effective panicles,number of grains per panicle,1000 grain weight and yield of rice decreased with the increase of the weed density.The effect of E.crusgalli and E.japonica on rice yield was mainly direct effect,and the degree of influence was different.The power function y=0.2776x0.8806+1.7851 was the best way to fit the relationship between E.japonica density and rice yield loss rate.The quadratic curve y=0.0159x2+2.3565x-0.8532 was used to fit the relationship between E.crusgalli density and rice yield loss rate,and the quadratic curve y=-0.0183x2+2.5255x-2.8411 was best model on the loss of rice yield caused by E.japonica+ E.crusgalli grew togather.When the cost of weeding was the same and 10%metamifop emulsifiable concentrate was applied respectively to control E.japonica,E.crusgalli and two mixed growth weeds,the economic infestation levels（EIL）were 2.77%～3%、2.07%～2.24%and 2.3%～2.49%,and the eco-economic threshold are 4.21～5.29 plants/m2,1.25～1.32 plants/m2 and 2.07～2.15 plants/m2 respectively.2.The control effects of 6 foliar treatment herbicides on 14 populations of E.japonica was determined at 2-leaf stage.The results showed that the efficacy reached 100%at 3825 g a.i./hm2 of propanil,180 g a.i./hm2 of metamifop,or at 450 g a.i./hm2 of cyhalofop-butyl.The control effects of halauxifen-methyl,quinclorac and quintrione were poor,propanil and metamifop were suitable for controlling E.Japonica.3.The combined effect of metamifop and fluroxypyr on the control of 2-leaf stage E.japonica showed that the values of objective efficacy（E0）reduced the theoretical efficacy（E）（E0-E）of metamifop+fluroxypyr（30+15 g a.i./hm2,30+30 g a.i./hm2）were more than 10%among the 25 mixed dose combinations,which showed synergistic.The the other values of（E0-E）were between-10%～10%,which showed additive.Therefore,the combined effect of metamifop and fluroxypyr against E.japonica was additive.The similar evaluation results of the combined effect for controlling 6-leaf stage E.japonica was obtained,it showed an additive effect.Experiment on the mixture of propanil,metamifop and fluroxypyr to control 6-leaf stage E.japonica showed that the fresh weight control effect of E.japonica reached 94.9%when the mixture of propanil+metamifop+fluroxypyr（2040 g a.i./hm2+15 g a.i./hm2+30 g a.i./hm2）,the efficacy was by 100%when the mixture of propanil+metamifop+fluroxypyr（2040 g a.i./hm2+60 g a.i./hm2+60 g a.i./hm2）applied.Therefore,the dosage of propanil+metamifop+fluroxypyr is（2040+（15～60）+（30～60））g a.i./hm2 was sugguested to effectively control E.japonica at 6-leaf stage.The combination of propanil,metamifop and fluroxypyr on the control E.japonica was evaluateed with Colby’s method.The value of the percentage of fresh weight（PTH）reduced the percentage of theoretical fresh weight（PA）on the propanil+metamifop+fluroxypyr（510+15+30 g a.i./hm2,510+15+45 g a.i./hm2）were greater than 10%,which showed synergistic.The（PTH-PA）values of other dose combinations was between-10%and 10%,which was additive. |
PDF Full Text Request