| ABSTRACT | 第8-9页 |
| 摘要 | 第10-19页 |
| Chapter 1 Introduction and Review of Literature | 第19-27页 |
| 1.1 Background and problem statement | 第19-20页 |
| 1.2 Justification and Significance of Research | 第20-21页 |
| 1.3 Review of Literature | 第21-25页 |
| 1.3.1 Nitrification process | 第21页 |
| 1.3.2 Why nitrate is a problem? | 第21-22页 |
| 1.3.3 Factors affecting nitrification process | 第22页 |
| 1.3.4 Soil acidification and CO_2 emission | 第22-23页 |
| 1.3.5 Nitrate accumulation, residual N and groundwater pollution | 第23-24页 |
| 1.3.6 Importance of nitrification inhibition in agricultural systems | 第24-25页 |
| 1.4 Research objectives | 第25页 |
| 1.5 Research contents and objectives | 第25-27页 |
| Chapter 2 Materials and Methods | 第27-34页 |
| 2.1 Site Description | 第27页 |
| 2.2 Experimental Design | 第27-34页 |
| 2.2.1 Field Experiment | 第27-31页 |
| 2.2.2 Incubation Experiment | 第31-34页 |
| Chapter 3 Dicyandiamide application improved nitrogen use efficiency and decreasednitrogen losses in wheat-maize crop rotation in Loess Plateau | 第34-45页 |
| 3.1 Introduction | 第34-36页 |
| 3.2 Results | 第36-42页 |
| 3.2.1 Soil pH and EC | 第36-37页 |
| 3.2.2 Mineral-N in Surface Soil | 第37-39页 |
| 3.2.3 NO_3~--N in Soil Profile (0-200 cm) | 第39页 |
| 3.2.4 Chlorophyll Contents (SPAD)and Aboveground Biomass | 第39-40页 |
| 3.2.5 Grain Yield and N Uptake | 第40-41页 |
| 3.2.6 NUE and N Surplus | 第41-42页 |
| 3.3 Discussion | 第42-45页 |
| 3.3.1 Effectiveness of DCD in reducing nitrification process | 第42-43页 |
| 3.3.2 DCD role in reducing nitrate leaching | 第43页 |
| 3.3.3 Effect of DCD application on plant growth and NUE | 第43-45页 |
| Chapter 4 Dicyandiamide increased ammonia volatilization and decreased carbondioxide emission from calcareous soil during wheat-maize rotation in Loess Plateau | 第45-55页 |
| 4.1 Introduction | 第45-46页 |
| 4.2 Results | 第46-52页 |
| 4.2.1 Soil pH | 第46-47页 |
| 4.2.2 Soil NH_4~+-and NO_3~--N | 第47页 |
| 4.2.3 NH3 volatilization | 第47-49页 |
| 4.2.4 CO_2 emission | 第49-52页 |
| 4.3 Discussion | 第52-55页 |
| 4.3.1 Effects ofN application rates and DCD on NH_3 volatilization | 第52页 |
| 4.3.2 Effects of N levels and DCD on CO_2 emission | 第52-55页 |
| Chapter 5 Evaluation of residual effect of nitrogen and dicyandiamide on wheat-maizecrop rotation in Loess Plateau | 第55-65页 |
| 5.1 Introduction | 第55-57页 |
| 5.2 Results | 第57-62页 |
| 5.2.1 Mineral-N in Soil Profile | 第57-60页 |
| 5.2.2 Chlorophyll Contents (SPAD) | 第60页 |
| 5.2.3 Yield and Aboveground Plant Biomass | 第60-61页 |
| 5.2.4 N Uptake by Crops | 第61-62页 |
| 5.3 Discussion | 第62-65页 |
| 5.3.1 Effect of residual N on grain yield and N uptake | 第62-63页 |
| 5.3.2 Changes in residual N in soil profile | 第63页 |
| 5.3.3 Movement Of NO_3~--N contents in soil profile | 第63-65页 |
| Chapter 6 Dicyandiamide degradation at different temperature and moisture levelsinfluenced greenhouse gases and ammonia emission from calcareous soil | 第65-80页 |
| 6.1 Introduction | 第65-67页 |
| 6.2 Results | 第67-76页 |
| 6.2.1 Soil pH | 第67-68页 |
| 6.2.2 Soil EC | 第68-69页 |
| 6.2.3 Mineral N | 第69-71页 |
| 6.2.4 NH_3 volatilization | 第71-72页 |
| 6.2.5 N_2O emission | 第72-73页 |
| 6.2.6 CO_2 emission | 第73-74页 |
| 6.2.7 DCD concentration & correlation with soil parameters | 第74-76页 |
| 6.3 Discussion | 第76-80页 |
| 6.3.1 Effect of N and DCD on nitrification process at different temperature and moisturelevels | 第76-77页 |
| 6.3.2 Effects of N and DCD on NH_3 volatilization | 第77-78页 |
| 6.3.3 Effects of N levels and DCD on N_2O emission | 第78页 |
| 6.3.4 Effects of N levels and DCD on CO_2 emission | 第78-80页 |
| Chapter 7 Summary | 第80-82页 |
| 7.1 Main conclusions | 第80页 |
| 7.2 Innovative points of study | 第80页 |
| 7.3 Suggestions and recommendations | 第80-82页 |
| References | 第82-98页 |
| ABOUT THE AUTHOR | 第98-99页 |
| RESEARCH PUBLICATIONS | 第99-100页 |
| ACKNOWLEDGEMENT | 第100页 |
