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AGRICULTURAL NONPOINT SOURCE POLLUTION: Watershed Management and Hydrology - Chapter 3

Nitơ là một trong các chất dinh dưỡng quan trọng cho tất cả các sinh vật sống và một trong những yếu tố quan trọng hạn chế năng suất cây trồng. Vì vậy, những nỗ lực nghiên cứu đáng kể được thực hiện trong những năm qua, cố gắng để làm sáng tỏ tất cả các quy trình kiểm soát N đi xe đạp trong các hệ sinh thái khác nhau. Các chu trình sinh địa hoá N là rất phức tạp bởi vì N có thể xảy ra ở các tiểu bang đường viền bằng vải nhiều tùy thuộc vào tiềm năng oxi. | 3 Nitrogen and Water Quality William F. Ritter and Lars Bergstrom TABLE OF CONTENTS 3.1 The Nitrogen Cycle 3.1.1 Mineralization and Immobilization 3.1.2 Plant N Uptake 3.1.3 Leaching and Surface Runoff 3.1.4 Ammonia Volatilization and Denitrification 3.2 Sources of Groundwater Contamination 3.2.1 Fertilizers 3.2.2 Livestock Wastes 3.2.3 Land Application of Manures Sludges and Wastewater 3.3 Sources of Surface Water Contamination 3.3.1 Fertilizers 3.3.2 Animal Wastes 3.3.3 Land Application of Manures and Sludges 3.4 Groundwater-Surface Water Interactions 3.5 Riparian Zone Processes 3.6 Effect of Tillage On Fate And Transport of Nitrogen 3.6.1 Surface Water 3.6.2 Groundwater 3.7 Whole Farm Nitrogen Budgets 3.8 Nitrogen and Water Management Practices to Reduce Nonpont Source Pollution 3.8.1 Nitrogen Management Practices 3.8.1.1 Accounting For All Sources 3.8.1.2 Realistic Yield Goals 3.8.1.3 Amounts of Nitrogen To Apply 3.8.1.4 Timing of Application 3.8.1.5 Calibration of Equipment 3.8.1.6 Early Season Soil And Plant Nitrate Tests 3.8.1.7 Nitrification Inhibitors 3.8.1.8 Leaf Chlorophyll Meters 2001 by CRC Press LLC 3.8.1.9 Cover Crops 3.8.2 Water Management 3.8.2.1 Irrigation Method 3.8.2.2. Drainage Volume 3.8.2.3 Irrigation Scheduling 3.9 Summary References 3.1 THE NITROGEN CYCLE Nitrogen is one of the major nutrients for all living organisms and one of the most important factors limiting crop yield. Therefore considerable research efforts have been undertaken over the years trying to elucidate all the processes controlling N cycling in various ecosystems. The biogeochemical N cycle is very complex because N can occur in many valance states depending on redox potential. Certain processes occur only aerobically and others only anaerobically regulated to a large extent by microbial processes occurring in a complex soil structure under nonsteady-state conditions. Because of its importance for crop yields high amounts of N are usually given to soils in agricultural .