Book Description

Development of management practices that reduce nitrogen (N) losses from agricultural lands has been the focus of research over many years. Development and testing of such practices is a complex task since it requires understanding of N dynamics in the soil-water-plant system, which is regulated by a large number of interacting physical, chemical, and biological processes. Nitrogen models are useful tools for developing and evaluating management practices for sustainable agriculture. The model, DRAINMOD-N was originally developed to simulate N dynamics in artificially drained soils. However, the model was based on a simplified N cycle, which restricted its applicability. A new version of DRAINMOD-N, referred to as DRAINMOD-N II, was developed and field-tested in this study. DRAINMOD-N II simulates N dynamics and turnover in the soil-water-plant system under different management practices and soil conditions. It considers a detailed N cycle, adds a simplified carbon cycle, and operates at different levels of complexity according to the conditions of the system being simulated. Processes considered in the model are atmospheric deposition, application of mineral N fertilizers, soil amendment with organic N sources, plant uptake, mineralization, immobilization, nitrification, denitrification, ammonia volatilization, and N losses due to leaching and surface runoff. DRAINMOD-N II driving hydrologic variables are predicted by the water management model DRAINMOD 5.1. DRAINMOD-N II was tested with a six-year data set from the North Carolina Lower Coastal Plain. The experimental site consists of eight 1.7-hectare instrumented, subsurface drained plots. The site was planted to a corn-wheat-soybean rotation. Water table depth (WTD) midway between the drains, subsurface drainage flow rates, and meteorological data were automatically measured and recorded. Flow proportional drainage water quality samples were collected and analyzed to determine N concentrations and loads. Results.