| The main content of this paper was the long term effect of rice-duck farming on weed control in experiment field which based on the previous study from 2000 to 2013 and continued to 2015.The results showed that the total density of weed seed bank decreased by 97.07%compared with the first year after 15 years' rice-duck farming in which seed bank of broad-leaf weed and sedge weeds decreased beyond 97%,the decrease amplitude of seed bank of grass weeds was the smallest that only decreased by 91.40%.From the whole observation of seed bank density,the decrease amplitude of weeds in wheat field was smaller than in paddy field.In the vertical level,the distribution of weed seed bank density which the upper layer was greater than middle layer and middle layer was greater than lower layer in the original changed to uniformly distributed among the three layers and obviously decreased compared with the first year's rice-duck farming.The total seed bank density decreased rapidly in the first seven years'rice-duck farming then fluctuated at a low level.Variation of seed bank density of broad-leaf weeds,grass weeds,sedgeweeds,summer weeds and winter weeds were also analyzed and the results showed that they had the same changing trend with the total seed bank density.The application of rice-duck farming controlled weeds well in paddy field,the control effect of most weeds in paddy field reached 100%in the first year's rice-duck farming.Based on continuous rice-duck farming,in order tofurther exhaust the weed seedbank,rice-duck farming combining with different weed control measures that were conventional rice-duck farming(RDF),rice-duck farming combining with seed removing and intercepting(RDF+RI),rice-duck farming combining with seed intercepting(RDF+I)and rice-duck farming combining with sowing in drill and ditching were studied(RDF+D).Results showed that the exhaustion effects of total weed seed bank were different under different weed control measures,among them total seed bank density decreased the most quickly under RDF+RI,then was under RDF+I,RDFand RDF+D.Therelative importance values of Rotala indica,Alopecurus japonicas and Alopecurus aequalis increased but therelative importance values of Echinochloa crusgalliLudwigia prostrata decreased after three years' RDF.Therelative importance values of A.japonicas and A.aequalis decreased but therelative importance values of E.crusgalli,R.indica and Monochoria vaginalis increased after three years' RDF+RI.Therelative importance values of A.japonicas,A.aequalis and E.crusgalli decreased but therelative importance values ofR.indica and M.vaginalis increased after three years' RDF+I.Therelative importance values of A.japonicas,A.aequalis,R.indica and E.crusgalli increased after three years'RDF+D.By comparing the datas,we found that there were different effects of RDF on different weed seeds in the soil and weed species on the ground,therefore,predation of duck to different weeds seed were studied.Results showed that duck had different predation to different weed seeds that duck had stronger predation to E.crusgalli and M.vaginalis,poor predation to Cyperus dfformis,Ammannia baccifera,R.indicand Leptochloa chinens is During six ours'feeding,the consumption ratio of E.crusgalli and M.vaginaliswere9l%?79%,respectively while the consumption ratio of C.difformis,A.baccifera,R.indicaand L.chinensis were 28%,20%,9%and 8%,respectively.Attempted discussion of the effect of duck predation on the reduction of weed seed bank density was also conducted. |
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