الفهرس 
Nitrogen Balance SimulationsOnly 14 pages are availabe for public view
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Abstract
Artificial drainage has helped in converting millions of hectares of flooded wetlands and swamps to highly productive soils. However, agricultural drainage effluent enriched with nutrients has resulted in severe ground and surface water contamination. Process-based simulation models of agricultural systems have been valuable tools for assessing the long-term impacts of different management practices on land productivity and water quality at both field and watershed scales. Upon entering the 21st century, however, more threats and challenges are confronting food security, land and water resources, in addition to the increasing concerns about climate change and global warming. This emphasizes the critical need for developing whole-system models which can help the design of effective water and nutrient management practices that reduce nitrogen (N) drainage losses and maintain high agricultural productivity under the anticipated scenarios of climate change and water availability. Most of the available models; however, emphasize certain processes in the agronomic ecosystems.
DRAINMOD and DRAINMOD-NII are widely used field-scale models for simulating the hydrology and water quality in artificially drained soils under wide variations of environmental conditions and management practices. However, they lack a mechanistic crop model that accounts for the effects of variations in seasonal weather conditions and soil nutrient status on crop phenological development and growth rate. DRAINMOD-W, a DRAINMOD-based watershed-scale model, uses flow-based site specific regression equations to estimate edge of field loads that neglects.