Main Ecological Environmental Effects And Functional Mechanism Of Rice-Duck-Azolla Integrated Farming

Rice field of gleyization and swampiness is a largest manual wetland ecological system,it is called "a gene pool of living things" because of its multi-ecological functions, for instance,cleansing sewage and beautifying environment.But its ecological function and productivity declined because that human being excess disturbing it and increasing its utilization and exploitation for economy benefit.Rice-duck integrated farming is an ecology agricultural pattern to adapt to agricultural development status,it is ecological engine system and can control ecological pollution in conventional rice production region.1,Effects of rice-duck integrated farming on rice plant were studied.We examined the stimulation effects of different rice-growing systems on rice plant by the field experiment in Dongtai experimental station of Nanjing Agricultural University,Jiangsu Province. Results showed that rice plant shape apparently changed because of ducks' activity in rice paddy.Carbohydrate content,C/N ratio and dry matter transfer ratio in stem were higher than control system.Basal internodes length,stem thick,stem mechanical strength and stem lodging resistant index were 2.88%,64.90%,11.78%and 10.95%higher than control system,respectively.Rice-duck integrated farming increased deep layer root ratio and root activity,but decreased black root ratio 16.63%than control system.2,Rice-duck integrated farming availability improved physichemical characters of soil and water,compared to CK treatment,soil surface layer's bulk density decreased 5.30%, total porosity increased 2.52%and non-capillary porosity increased 19.03%.Organic matter,available N,P,K increased 6.41%,9.74%,5.24%and 5.17%,respectively compared to CK treatment.Total N,P,K of water also increased 9.31%,16.46%and 16.42%.So these results showed that duck dejection can significantly increase water nutrition content,and significantly improve yield characters and quality items.Panicle length of rice-duck integrated farming was 1.41%longer than CK treatment and harvest index hoist 5.48%.Through rice quality items analyzing,brown rice,milled rice,and head rice ratio increased 3.21%,4.82%,3.49%in RD treatment compared to CK treatment,but chalkness decreased 26.17%,amylose content increased 4.03%,gel consistency increased 9.06%,and albumin,glutelin content increased 12.12%and 13.35%respectively.3,This article makes research on the ecological effects of rice-duck integrated farming on developing regularity of flee diseases,insects and weeds.The research finds that rice-duck integrated farming can prevent 96.1%of the weeds from growing,thus reducing the varieties of the weeds,although the Pielou evenness index rises.Rice-duck integrated farming has visible ecological effect on control over brown planthoppers,and the total prevention rate reaches 65.49%.By adopting rice-duck integrated farming,the ducks prey on spiders,which reduces the numbers of spiders,as a result,the ratio between spiders and brown planthoppers is increased.Although ducks have some control effect on Cnaphalocrocis medinalis Guenee and Chilo suppressalis Walker,their control ability over such insects will be weakened with the growth of rice plants.Thanks to the ducks, rice-duck integrated farming can cut down the occurrence rate of rice stripe disease event if this method cannot fully prevent the disease from arising.Besides,rice-duck integrated farming can also effectively control rice blast,and the prevention rate reaches 57.02%.Rice stripe disease transmitted by brown planthopper is one of the most serious viral disease in some rice-growing areas of China in recent years.As an ecological practice of rice growing, rice-duck integrated farming has shown great effects on the controls of rice insects, diseases and weeds.However,there is no direct field evidence of the integrated farming effects on brown planthopper and rice stripe disease.Here we examined the effects of different rice-growing systems on controlling brown planthopper population and rice stripe disease in field experiments in Dongtai experimental station of Nanjing Agricultural University,Jiangsu Province,China.The treatments included Conventional rice production system,Rice-duck integrated system,Rice-duck integrated system with insect proof net during seedling stage and Control system.Results showed that the RD and NRD treatments significantly reduced brown planthopper population,resulting in great decline in the incidence of rice stripe disease during all stages of rice growth.The highest reduction in brown planthopper population was found in the NRD treatment with over 94.01% reduction of rice stripe disease.The RD treatment decreased rice stripe disease incidence by 79.44%,higher than that in CR treatment(78.82%).The findings suggest that rice-duck integrated farming,especially plant covered with insect proof net cover during the seedling stage,is a safe and high efficiently ecological approach for controlling rice stripe disease in China.4,Light machinery cultivation has many ecological function of decreasing labor and cost,but increasing economical effect.While these dee paddies had many weeds,and difficulties to control them.Weeds varieties in Manpower transplanted rice-duck integrated farming region(TRD) were lower than that in Direct seeding rice-duck integrated farming region(DSRD) and Machine-transplanted rice-duck integrated farming region(MTRD),but Shannon-wiener index is the highest in DSRD treatment.Weeds community constitution was Ludwigia prostrata+Ammannia baccifera L+Cyperus difformis in DSRD treatment, however,Echinochloa crusgalli and Leptochloa chinensis declined non-dominant weeds. Similarity index of weed communities was higher between in DSRD treatment and MTRD treatment,their weed varieties and Shannon-wiener index all higher than TRD treatment. But Wittaker index was the highest in TRD treatment.5,The article studied main eco-funetions of rice-duck-azolla mutualism compound system.Rice-duck-azolla integrated farming could improve soil fertility and the organic matter,available N,P,K increased 7.95%,7.05%,6.47%,4.46%than the CK treatment, respectively.The controlling effect of rice-duck-azolla integrated farming on weeds reached 98.94%,reduced the infestation of former dominant weed species and weed quantity,but evenness index rose.Rice-duck-azolla integrate farming had apparent controlling effects on planthopper,so decreased happening chances of rice stripe disease. Rice-duck-azolla integrate farming had significantly controlling effect on rice sheath blight, but it couldn't control the occurrence of rice sheath blight.6,Through ¹⁵N labeling technology analyzed azolla's N distribution dynamic, rice-duck-azolla integrated farming available improved rice field environment because of ducks's activity,¹⁵N recovery ratio of water,soil and rice plant in this treatment was all the highest,and azolla N losing ratio was only 11.20%,but rice-azolla treatment's azolla losing ratio reached 62.45%.So rice-duck-azolla integrated farming availability improved yield characters and quality items with the condition of azolla and duck dejecta supplied nutrition to rice yield.7,The ratio between direct physiological energy and manual supplementary energy were 34.39%,30.83%and 32.34%,in rice-duck-azolla integrated farming,rice-duck integrated farming and conventional rice production region,respectively.The ratio between organic energy and manual supplementary energy were 9.6%,2.8%å’Œ0.7%in the three treatments,respectively.The contents of N,P₂O₅,K₂O in rice-duck-azolla integrated farming had profit to some extent,but N content lost in dee-duck integrated farming and conventional rice production region,P₂O₅ and K₂O had profit.Flux of N,P₂O₅,K₂O in rice-duck-azolla integrated farming and rice-duck integrated farming were higher than that in conventional rice production region,this showed that the nutrient cycle degree were higher and low dependence on fertilization in the two treatments.