| 摘要 | 第6-8页 |
| ABSTRACT | 第8-10页 |
| CHAPTER 1 INTRODUCTION | 第19-31页 |
| 1.1 Nitrogen Use Efficiency | 第19-21页 |
| 1.2 Nitrogen mineralization | 第21-29页 |
| 1.2.1 Mechanism of nitrogen assimilation: | 第23-24页 |
| 1.2.2 Nitrate assimilation: | 第24页 |
| 1.2.3 Biotic immobilization–remineralization | 第24-25页 |
| 1.2.4 Abiotic Immobilization | 第25页 |
| 1.2.5 Soil organic nitrogen mineralization | 第25页 |
| 1.2.6 Gross and net N mineralization | 第25-26页 |
| 1.2.7 Soil N mineralization potential | 第26页 |
| 1.2.8 Factors affecting soil N mineralization | 第26-28页 |
| 1.2.9 Indexes of N mineralization | 第28-29页 |
| 1.3 Scientific Question | 第29页 |
| 1.4 Hypothesis | 第29页 |
| 1.5 Objectives | 第29-31页 |
| CHAPTER 2 MATERIALS AND METHODS | 第31-38页 |
| 2.1 Design or route map | 第31-32页 |
| 2.2 Site description,sampling | 第32-33页 |
| 2.2.1 Soil sample preparation for the analysis of basic properties | 第32页 |
| 2.2.2 Chemical and biological analysis of incubated and non-incubated soils | 第32-33页 |
| 2.3 Experimental setup | 第33-35页 |
| 2.3.1 Incubation study(N Mineralization) | 第33-34页 |
| 2.3.2 Pot experiment cropped with winter wheat and summer maize | 第34-35页 |
| 2.4 Chemical analysis | 第35-36页 |
| 2.5 Data processing and statistical analysis | 第36-38页 |
| CHAPTER 3 POT STUDY IN WINTER WHEAT“RELATION OF NUE WITH SOIL FERTILITY” | 第38-57页 |
| 3.1 Summary | 第38页 |
| 3.2 Introduction | 第38-39页 |
| 3.3 Results | 第39-53页 |
| 3.3.1 Crop yield | 第39-41页 |
| 3.3.2 Nitrogen uptake | 第41-42页 |
| 3.3.3 Nitrogen use efficiency | 第42页 |
| 3.3.4 Relationship between grain yield,NUE and soil fertility levels | 第42-43页 |
| 3.3.5 Chemical and biological changes in soil | 第43-53页 |
| 3.4 Discussion | 第53-57页 |
| 3.4.1 Crop yield | 第53页 |
| 3.4.2 Nitrogen uptake | 第53-54页 |
| 3.4.3 Nitrogen use efficiency | 第54页 |
| 3.4.4 Relationship between wheat grain yield and soil fertility levels,~(15)NUE in wheat and soil fertility levels | 第54-55页 |
| 3.4.5 NUE links with N mineralization | 第55页 |
| 3.4.6 Chemical and biological changes in soil | 第55-57页 |
| CHAPTER 4 POT STUDY IN SUMMER MAIZE“RELATION OF NUE WITH SOIL FERTILITY” | 第57-75页 |
| 4.1 Summary | 第57页 |
| 4.2 Introduction | 第57-58页 |
| 4.3 Results | 第58-71页 |
| 4.3.1 Crop yield | 第58页 |
| 4.3.2 Nitrogen uptake | 第58-61页 |
| 4.3.3 Nitrogen use efficiency | 第61-65页 |
| 4.3.4 Relationship between grain yield,NUE and soil fertility levels | 第65页 |
| 4.3.5 Chemical and biological changes in soil | 第65-71页 |
| 4.4 Discussion | 第71-75页 |
| 4.4.1 Crop yield | 第71-72页 |
| 4.4.2 Nitrogen uptake | 第72页 |
| 4.4.3 Nitrogen use efficiency | 第72-73页 |
| 4.4.4 NUE links with N mineralization study | 第73页 |
| 4.4.5 Chemical and biological changes in soil | 第73-75页 |
| CHAPTER 5 NITROGEN SUPPLY FROM SOIL THROUGH MINERALIZATION | 第75-88页 |
| 5.1 Summary | 第75页 |
| 5.2 Introduction | 第75-76页 |
| 5.3 Results | 第76-85页 |
| 5.3.1 Changes in NH_4~+-N and NO_3~-N content in the soil during the incubation | 第76页 |
| 5.3.2 N mineralization potential and mineralization rate constant(k) | 第76页 |
| 5.3.3 Net N mineralization rate and cumulative N mineralization rate | 第76-79页 |
| 5.3.4 Availability of mineralized N to wheat and maize during the whole growing period | 第79-81页 |
| 5.3.5 The relationship between N mineralization rate and soil microbial biomass | 第81页 |
| 5.3.6 Temporal changes in mineralized N and fixed NH4+ | 第81页 |
| 5.3.7 Nitrified nitrogen and k(constant)rate | 第81-85页 |
| 5.4 Discussion | 第85-88页 |
| 5.4.1 N mineralization process | 第85-86页 |
| 5.4.2 Fixation of mineralized NH4+ | 第86-87页 |
| 5.4.3 The quantitative relationship between mineralization and nitrification | 第87-88页 |
| CHAPTER 6 CONCLUSION | 第88-92页 |
| REFERENCES | 第92-106页 |
| ACKNOWLEDGEMENTS | 第106-108页 |
| CURRICULUM VITAE | 第108-109页 |
