Nitrogen management and ground water protection

Abstract

Dedication. List of Contributors. 1. Ground Water Quality Concerns About Nitrogen (R.F. Follett, D.J. Walker). Introduction. Health concerns. Human toxicity. Economic concerns. Economic concepts. Problem nature and implications for solution. Public policy options. Resource conservation concerns and issues. References. 2. Sources of Nitrate to Ground Water (D.R. Keeney). Introduction. Nitrogen cycling. Natural sources of nitrate. Geologic nitrogen. Forests. Forage and pasteral agriculture. Waste materials. Animal wastes. Sewage sludge and effluent. Septic tanks. Row crops agriculture. Irrigated agriculture. Summary. References. 3. Nitrate in Ground Water in the United States (G.R. Hallberg). Introduction. Nitrate, agriculture and ground water. Nitrate and water quality: a national overview. Comparisons with state data. Surface water and ground water. Nitrate distribution and variability. Depth distribution. Spatial variability and depth distribution. Spatial variability: land use and local sources. Temporal variations. Depth and time. Denitrification and time. Nitrate variability among wells. Summary and conclusions. References. 4. Ground Water Nitrate in Other Developed Countries (Europe) - Relationships to Land Use Patterns (S. Juergens-Gschwind). Introduction. Impact of bare land. Impact of forestry. Impact of grassland. Cut grassland (meadowland). Grazed grassland. Impact of arable crops. Depending on crop type. Depending on type of soil. Depending on rainfall and irrigation. Depending on temperature. Depending on ground water level and drainage. Depending on rate, timing and form of fertilizer use. The impact of horticulture. Intercropping and green manuring. Irrigation. Home and hobby gardens. References. 5. Nitrate Transport and Leaching Mechanisms (W.A. Jury, D.R. Nielson). Introduction. Nitrate transport mechanism. Convection. Diffusion. Hydrodynamic dispersion. Removal and reaction mechanisms. Plant uptake. Denitrification. Spatial variability and the transport problem. Models for characterizing leaching. Process models. Stochastic models. Spatial variability and the modeling problem. Uncertainty in modeling transport to ground water. Summary and conclusions. References. 6. Proper Accounting for N in Cropping Systems (J.F. Power, F.E. Broadbent). Introduction. Crop N requirements and yield goals. Contrubitions to residual soil N. Soil tests and residual nitrates. Management practices and N accounting. Mineralization and immobilization. Organic-inorganic interchange of N in soils. Kinetics of immobilization and mineralization. Factors influencing immobilization. Influence of environmental factors on immobilization and mineralization. Predicting N mineralization. Conceptual models of mineralization and immobilization. Conclusions. References. 7. Fertilizer Nitrogen Management (G.A. Peterson, W.W. Frye). Introduction. Importance of N fertilizer to agriculture. Amount of fertilizer-N to apply. Yield goals. Soil tests. Soil sampling.