声明
Dedication
List of Acronyms
Chapter 1. Introduction
1.1Background of the Study
1.2Factors responsible for high yield in maize
1.3Breeding efforts in maize yield improvement
1.4Agronomic efforts in maize yield improvement
1.5Hurdles and limitation in achieving yield potential
1.6Management practices to improve maize grain yield
1.6.1Nitrogen use efficiency and N uptake improvement through breeding
1.6.2Agronomic practices for N management in high density maize
1.7Problem statement
1.8Aims and objectives
Chapter 2. Materials and Methods
2.1Field Characteristics and Site Description
2.2Experimental Design and Treatment setup
2.3Plant material
2.4Agronomic Management and Plant Sampling
2.5Measurements and Calculations
2.5.1Plant sampling for leaf area, DMA and nutrient concentration
2.5.2Crop growth parameters
2.5.3Canopy light interception, Photosynthesis and SPAD measurements
2.5.4Grain filling duration and grain filling rate
2.5.5Yield and yield components
2.5.6 Soil Nmindetermination
2.5.7 Plant N analysis, N use efficiency(NUE) and NUE components
2.5.8 Statistical Methods and Analysis
Chapter 3.Yield, dry matter accumulation and canopy traits
3.1 Introduction
3.1.1An overview of maize agronomy under different managements
3.2 Results
3.2.1Grain yield and yield attributes
3.2.2Leaf area index and green leaf number
3.2.3Dry matter accumulation and dry matter partitioning
3.2.4Plant height, ear height and stem diameter
3.2.5Grain filling rate
3.3 Discussion
3.3.1Maize hybrids differ greatly for yield traits under nitrogen and density stress
3.3.2Characteristics of yield improvement under high density and high nitrogen
3.3.3Post–silking dry matter accumulation contributed more in hundred seed weight as a function of source–sink balance
3.3.4 Conclusion
Chapter 4. Photosynthesis and light distribution
4.1 Introduction
4.2 Results
4.2.1SPAD measurements
4.2.2Gaseous exchange measurements
4.2.3Light distribution within crop canopy
4.3 Discussion
4.3.1High N rate maintains SPAD and photosynthetic activity of maize hybrids
4.3.2High density and high N interplay for light distribution within crop canopy
4.3.3 Conclusion
Chapter 5.Plant nitrogen uptake and utilization efficiency
5.1 Introduction
5.2 Results
5.2.1Nitrogen use efficiency(NUE) and components of NUE
5.2.2N translocation and translocation efficiency
5.3 Discussion
5.3.1Characteristics of maize hybrids regarding N uptake and utilization efficiency
5.3.2High N rate and high planting density maximized the NUE
5.3.3 Conclusion
Chapter 6. Soil mineral nitrogen dynamics
6.1 Introduction
6.2 Results
6.2.1Ammonium–N (NH4–N) status in soil
6.2.2Nitrate–N (NO3–N) status in soil
6.3 Discussion
6.3.1Effects of N rates and plant density on soil ammonium N
6.3.2Effects of N rates and plant density on soil nitrate N
6.3.3 Conclusion
Chapter 7. Summary and Recommendations
参考文献
Appendix 1: Yield, dry matter accumulation and canopy traits
Appendix 2: Photosynthesis and light distribution
Appendix 3: Plant nitrogen uptake and utilization efficiency
Appendix 4: Soil mineral nitrogen dynamics
致谢
Curriculum Vitae
中国农业科学院;
