| 摘要 | 第6-8页 |
| abstract | 第8-9页 |
| Chapter 1 Introduction | 第12-31页 |
| 1.1 General overview | 第12-15页 |
| 1.2 Background | 第15页 |
| 1.3 The importance of nitrogen in agricultural system | 第15-17页 |
| 1.4 Basic nitrogen process in the soil-plant system | 第17-19页 |
| 1.5 Nitrogen cycle in agricultural system | 第19-21页 |
| 1.6 Role of nitrogen in plants | 第21页 |
| 1.7 Over use chemical nitrogen as a result of serious environmental problem | 第21-22页 |
| 1.8 N isotopes | 第22-25页 |
| 1.9 Basic composition of rice-duck co-culture system | 第25-26页 |
| 1.10 Effects of rice-duck co-culture on paddy field weeds | 第26页 |
| 1.11 Effects of rice-duck co-culture on soil fertility and soil microbes | 第26-27页 |
| 1.12 Stimulating effects of duck activities on rice plants | 第27页 |
| 1.13 Roles and functions of ducks on crop production | 第27-28页 |
| 1.14 Benefit analysis:Rice-duck co-culture | 第28页 |
| 1.15 Mutualism benefit on the interaction between rice and duck | 第28-30页 |
| 1.16 Aims and Hypothesis | 第30-31页 |
| Chapter 2 Materials and methods | 第31-38页 |
| 2.1 Field experiment | 第31-35页 |
| 2.1.1 Experimental site | 第31页 |
| 2.1.2 Agricultural activities and sampling record in2017 and | 第31-33页 |
| 2.1.3 Experimental design and operation | 第33-35页 |
| 2.2 N pot experiment | 第35页 |
| 2.3 Sampling and measurements | 第35-36页 |
| 2.4 Calculations | 第36页 |
| 2.5 Statistical analyses | 第36-38页 |
| Chapter 3 Results | 第38-61页 |
| 3.1 N and P concentration in the first rice season(2017) | 第38-40页 |
| 3.2 Effects of Organic Fertilizer in the Field | 第40-42页 |
| 3.3 Yield and Yield components at Ninghe experimental farm in2017 | 第42-43页 |
| 3.4 N concentration in rice season2 (2018) | 第43-46页 |
| 3.5 Interactive effect between duck level and treatment,year,duck level and treatment on N concentration in two consecutive rice seasons | 第46-50页 |
| 3.6 Pot experiment with Japonica rice varieties | 第50-57页 |
| 3.7 Total15N content | 第57-58页 |
| 3.8 N derived from the fertilizer and from the soil | 第58-60页 |
| 3.9 Fresh Grain15N,Husk15N Content,N Uptake,and N Use Efficiency | 第60-61页 |
| Chapter 4 Discussion | 第61-71页 |
| 4.1 Effect of duck presence on rice plant growth and rice yield | 第61-62页 |
| 4.2 Interactive effects of duck levels,treatment,and year and treatment on N concentration | 第62-63页 |
| 4.3 Importance of Organic Fertilizer in the Field | 第63-65页 |
| 4.4 Responses of N application on the growth of Japonica rice varieties in two soil types | 第65-67页 |
| 4.5 Influence of Ammonium Sulfate-15N in the Field,N derived from the fertilizer and from the soil with and without duck in the field | 第67-69页 |
| 4.6 Concentration of15N,N uptake,and N use efficiency | 第69-71页 |
| Chapter 5 General conclusion | 第71-74页 |
| 5.1 Main conclusions | 第71-73页 |
| 5.2 Perspectives and future directions | 第73-74页 |
| References | 第74-87页 |
| Appendices | 第87-119页 |
| Acknowledgements | 第119-120页 |
| Author Resume | 第120页 |
