声明
摘要
Abstract
CONTENTS
Abbreviations
CHAPTER Ⅰ General introduction
1.1 The importance of wheat production
1.2 The importance of corn production
1.3 Cropping system
1.4 Tillage and its effect on agricultural soils
1.4.1 Effect of tillage on bulk density
1.4.2 Soil organic carbon
1.4.3 Biological effect of tillage on soil
1.5 Crop productivity and tillage practices
1.6 Global warming
1.7 The component of greenhouse gas emission in agricultural soils
1.7.1 CO2
1.7.2 N2O
1.7.3 CH4
1.8 Objectives
CHAPTER Ⅱ The effects of tillage on crop yield and yield components
2.1 Introduction
2.2 Materials and methods
2.2.1 Experimental site
2.2.2 Experimental design and management
2.2.3 Plant sampling and determinations
2.2.4 Data analysis
2.3 Results
2.3.1 Wheat yield and yield components
2.3.2 Wheat aboveground biomass
2.3.3 Leaf area index at flowering stage wheat
2.3.4 Corn yield and yield components
2.3.5 Leafarea index at flowering stage of corn
2.3.6 Annual yield
2.4 Discussion
2.5 Conclusion
CHAPTER Ⅲ Nitrogen use efficiency in a wheat-corn cropping system
3.1 Introduction
3.2 Materials and methods
3.3 Results
3.3.1 Tillage effects on nitrogen uptake and use efficiency in wheat
3.3.2 The tillage effects on nitrogen uptake and use efficiency in corn
3.3.3 Annual effects of tillage on nitrogen uptake and use efficiency
3.4 Discussion
3.5 Conclusion
CHAPTER Ⅳ Soil Characteristics
4.1 Introduction
4.2 Materials and methods
4.2.1 Soil sampling
4.2.2 Soil Bulk density
4.2.3 Soil nitrate (NO3--N) and ammonium (NH4+-N)
4.2.4 Soil pH
4.2.5 Measurements of microbial biomass C and N
4.2.6 Soil organic carbon (SOC)
4.2.7 Soil total nitrogen (TN)
4.2.8 Soil Denitrification capacity
4.2.9 Soil nitrification potential
4.3 Results
4.3.1 Impact of tillage on soil bulk density in wheat growth period
4.3.2 Impact of tillage on soil bulk density in corn growth period
4.3.3 Impact of tillage on water holding capacity at the corn maturity stage
4.3.4 Soil moisture
4.3.5 Impact of tillage practices on total N content of soil in wheat
4.3.6 Impact of tillage practices on total N content of soil in corn
4.3.7 Microbial biomass carbon content of soil during wheat growing season
4.3.8 Soil microbial biomass N content during wheat growing season
4.3.9 Soil organic carbon content at maturity stage of wheat
4.3.10 Impact of tillage practices on ratio of C/N at maturity stage of wheat
4.3.11 Soil organic carbon content of soil at maturity stage of corn
4.3.12 The soil concentration of ammonium during wheat growing season
4.3.13 Soil concentration of nitrate during wheat growing season
4.3.14 Soil nitrification capacity
4.3.15 Soil denitrification capacity
4.3.16 Soil pH at wheat maturity
4.3.17 Soil pH at corn maturity
4.4 Discussion
4.5 Conclusion
CHAPTER Ⅴ Whole year gas emissions in corn-wheat cropping system
5.1 Introduction
5.2 Materials and methods
5.2.1 Gas sampling and measurement
5.2.2 GWP of CH4 and N2O
5.3 Results
5.3.1 Annual N2O fluxes in corn-wheat cropping
5.3.2 Annual CH4 fluxes and emission in corn-wheat cropping
5.3.3 Area-scaled GWP and yield-scaled GWP
5.4 Discussion
5.5 Conclusion
CHAPTER Ⅵ Conclusion and suggestion
6.1 Conclusion
6.2 Suggestions
REFERENCES
ACKNOWLEDGEMENTS
AUTHOR’S BIOGRAPHY HOJATOLLAH LATIFMANESH