Studies On Function Of Mitigating Methane Emission In Paddyfield And Imporvement Of Rice Growth Environment In Rice-Duck-fish Complex Ecosystem

To combine raising fish in paddy field and feeding duck in open in paddy field and form a new kind of compounded ecosystem, and make paddy- the biggest primary producer in rice field and fish, duck-the greatest consumers band together organically, and form a benign and high efficiency compounded ecosystem which rice, duck and fish live together. The study made systematically on rice-duck-fish compounded ecosystem from the aspects of the discharge of CH4 in paddy-field, the physical character of soil condition of paddy-field, the main chemical property of water, the growth properties of paddy plants and so on, and at the same time made a research and analysis on the emergence and development of paddy's main diseases and insect pests in the compounded ecosystem and established the relevant mathematical model. The results of research are listed below:1. In rice-duck-fish compounded ecosystem, during the period of their growing and raising, the discharge of CH4 presented a certain of rules, the two discharge peaks were respectively at the stage of paddy's returning green and at the stage of spike differentiation, the first peak was 15.813 mg/m2.h and the second was 9.485 mg/m2.h, next at the full tiller stage, the discharge of CH4 could reach the highest at 8.227 mg/m2.h. In the rice-duck-fish compounded ecosystem, fishes and ducks can reduce the discharge of CH4 by controlling weeds and clearing away the bottom leaves of rice made effects on the condition which the methanogens living in; The activity of fishes and ducks can increase the dissolved oxygen of water and soil of paddy-field, improve the oxidation/reduction of soil, impulse the oxidation speed of methanogens, and all of these have reduced the emission flux and emission gross, and have an obvious controllable effect on discharge of CH4 at peak period.2. In rice-duck-fish complex ecosystem, the environmental of soil gets obvious improvement. Soil oxidation-reduction potential increased 10.98 mv , reduced material total amount, activation reduced material total amount reduced 1.46cmol/kg , 1.25cmol/kg respectively.3. Rice-duck-fish complex ecosystem can obviously improve the content of quick acting nitrogen, quick-acting phosphorus, and organic matter. In rice-duck-fish area, the content of quick acting nitrogen in soil increased 14.6mg/kg than that in CK, the quick acting potassium is 11.02mg/kg higher than in CK, and the quick-acting phosphorus added 1.0mg/kg than that in CK; In rice-duck-fish area, soil organic matter is 1.31g/kg higher than that in CK. The organic matter content of soil reduced in rice-fish area is 0.61g/kg higher than that in CK.4. Under rice-duck-fish treatment, soil unit weight has reduced 0.02g/cm3 than under rice-fish treatment, reduced 0.12g/cm3 than under CK treatment. Raising duck or raising fish in rice field can clearly improve soil physics properties and the soil aeration.5. In complex ecosystem, dissolved oxygen (D.O.) has showed obvious diurnal change laws. The general trend is the concentrations of D.O. in water increased with raising of temperature. At afternoon 2:00 it reached max., and then reduced. On the next day morning at 6:00 the D.O in water was the lowest. The study showed that thecommensalisms of rice-duck-fish and rice-fish can greatly increase D.O. in water and related with the temperature. The differences of D.O. under the three treatments reached an extremely obvious level. In water the concentration of NH4+, S^2- and pH value of water changed gently day in value.6. The control effects of rice-duck-fish commensalisms on rice planthoppers: the control effect on rice planthoppers in rice-duck-fish area is better than the effects in rice-fish area and pesticide usage area. In pesticide usage area the amount of rice planthoppers have reduced sharply after the application of pesticide but at the same time, the application of pesticide have killed the natural enemy of rice planthoppers, so when the effects of pesticide faded the amount of rice planthoppers raised obviously. In order to control the rice...