| 摘要 | 第6-8页 |
| Abstract | 第8-10页 |
| Abbreviations | 第18-20页 |
| CHAPTER I General introduction | 第20-31页 |
| 1.1 The importance of wheat production | 第21-22页 |
| 1.2 The importance of corn production | 第22-23页 |
| 1.3 Cropping system | 第23-25页 |
| 1.4 Tillage and its effect on agricultural soils | 第25-27页 |
| 1.4.1 Effect of tillage on bulk density | 第26页 |
| 1.4.2 Soil organic carbon | 第26-27页 |
| 1.4.3 Biological effect of tillage on soil | 第27页 |
| 1.5 Crop productivity and tillage practices | 第27-28页 |
| 1.6 Global warming | 第28页 |
| 1.7 The component of greenhouse gas emission in agricultural soils | 第28-30页 |
| 1.7.1 CO_2 | 第28-29页 |
| 1.7.2 N_2O | 第29页 |
| 1.7.3 CH_4 | 第29-30页 |
| 1.8 Objectives | 第30-31页 |
| CHAPTER II The effects of tillage on crop yield and yield components | 第31-48页 |
| 2.1 Introduction | 第31页 |
| 2.2 Materials and methods | 第31-34页 |
| 2.2.1 Experimental site | 第31-32页 |
| 2.2.2 Experimental design and management | 第32-33页 |
| 2.2.3 Plant sampling and determinations | 第33-34页 |
| 2.2.4 Data analysis | 第34页 |
| 2.3 Results | 第34-45页 |
| 2.3.1 Wheat yield and yield components | 第34-36页 |
| 2.3.2 Wheat aboveground biomass | 第36-38页 |
| 2.3.3 Leaf area index at flowering stage wheat | 第38页 |
| 2.3.4 Corn yield and yield components | 第38-42页 |
| 2.3.5 Leaf area index at flowering stage of corn | 第42-43页 |
| 2.3.6 Annual yield | 第43-45页 |
| 2.4 Discussion | 第45-46页 |
| 2.5 Conclusion | 第46-48页 |
| CHAPTER III Nitrogen use efficiency in a wheat–corn cropping system | 第48-56页 |
| 3.1 Introduction | 第48页 |
| 3.2 Materials and methods | 第48-49页 |
| 3.3 Results | 第49-54页 |
| 3.3.1 Tillage effects on nitrogen uptake and use efficiency in wheat | 第49-52页 |
| 3.3.2 The tillage effects on nitrogen uptake and use efficiency in corn | 第52-53页 |
| 3.3.3 Annual effects of tillage on nitrogen uptake and use efficiency | 第53-54页 |
| 3.4 Discussion | 第54-55页 |
| 3.5 Conclusion | 第55-56页 |
| CHAPTER IV Soil Characteristics | 第56-82页 |
| 4.1 Introduction | 第56-57页 |
| 4.2 Materials and methods | 第57-59页 |
| 4.2.1 Soil sampling | 第57页 |
| 4.2.2 Soil Bulk density | 第57页 |
| 4.2.3 Soil nitrate (NO_3~--N) and ammonium (NH_4~+-N) | 第57页 |
| 4.2.4 Soil p H | 第57-58页 |
| 4.2.5 Measurements of microbial biomass C and N | 第58页 |
| 4.2.6 Soil organic carbon (SOC) | 第58页 |
| 4.2.7 Soil total nitrogen (TN) | 第58页 |
| 4.2.8 Soil Denitrification capacity | 第58-59页 |
| 4.2.9 Soil nitrification potential | 第59页 |
| 4.3 Results | 第59-78页 |
| 4.3.1 Impact of tillage on soil bulk density in wheat growth period | 第59-60页 |
| 4.3.2 Impact of tillage on soil bulk density in corn growth period | 第60-61页 |
| 4.3.3 Impact of tillage on water holding capacity at the corn maturity stage | 第61页 |
| 4.3.4 Soil moisture | 第61-62页 |
| 4.3.5 Impact of tillage practices on total N content of soil in wheat | 第62-64页 |
| 4.3.6 Impact of tillage practices on total N content of soil in corn | 第64-65页 |
| 4.3.7 Microbial biomass carbon content of soil during wheat growing season | 第65-66页 |
| 4.3.8 Soil microbial biomass N content during wheat growing season | 第66-67页 |
| 4.3.9 Soil organic carbon content at maturity stage of wheat | 第67-68页 |
| 4.3.10 Impact of tillage practices on ratio of C/N at maturity stage of wheat | 第68-69页 |
| 4.3.11 Soil organic carbon content of soil at maturity stage of corn | 第69-70页 |
| 4.3.12 The soil concentration of ammonium during wheat growing season | 第70-72页 |
| 4.3.13 The soil concentration of nitrate during wheat growing season | 第72-74页 |
| 4.3.14 Soil nitrification capacity | 第74-75页 |
| 4.3.15 Soil denitrification capacity | 第75-76页 |
| 4.3.16 Soil p H at wheat maturity | 第76-77页 |
| 4.3.17 Soil p H at corn maturity | 第77-78页 |
| 4.4 Discussion | 第78-80页 |
| 4.5 Conclusion | 第80-82页 |
| CHAPTER V Whole year gas emissions in corn-wheat cropping system | 第82-97页 |
| 5.1 Introduction | 第82-83页 |
| 5.2 Materials and methods | 第83-84页 |
| 5.2.1 Gas sampling and measurement | 第83页 |
| 5.2.2 GWP of CH_4 and N_2O | 第83-84页 |
| 5.3 Results | 第84-95页 |
| 5.3.1 Annual N_2O fluxes in corn-wheat cropping | 第84-88页 |
| 5.3.2 Annual CH_4 fluxes and emission in corn-wheat cropping | 第88-90页 |
| 5.3.3 Area-scaled GWP and yield-scaled GWP | 第90-95页 |
| 5.4 Discussion | 第95-96页 |
| 5.5 Conclusion | 第96-97页 |
| CHAPTER VI Conclusion and suggestion | 第97-103页 |
| 6.1 Conclusion | 第97-102页 |
| 6.2 Suggestion | 第102-103页 |
| REFERENCES | 第103-117页 |
| ACKNOWLEDGEMENTS | 第117-119页 |
| AUTHOR’S BIOGRAPHY | 第119页 |
