The Nitrogen Simulation Model, DRAINMOD-N II: Field Testing and Model Application for Contrasting Soil Types and Climatological Conditions

DRAINMOD-N II is a field-scale, process-based model that simulates nitrogen dynamics and turnover in drained croplands under different management practices and soil and environmental condition. This paper summarizes results of testing the model using data sets from two drained agricultural sites with contrasting soils, climatic conditions, and management practices. One site is located in North Carolina and the other site is located in Indiana. It also summarizes results of long term simulations conducted using calibrated model inputs to study the effects of drainage design and management and N fertilization rates on NO₃-N leaching losses under the local soil and climatic conditions of each site. Results of the two field evaluations indicated that the model accurately predicted annual and cumulative NO₃-N losses from both sites. Model predictions for the IN site were more accurate than model predictions for the NC site. Results of the long term simulation studies demonstrated the strong influence of the N fertilization rates on N losses from drained croplands. It also indicated the influence of drainage design (drain depth and spacing) and management (drainage control) on N leaching losses. The predicted response of the soil-water-plant system at each site to different drainage water and N fertilization scenarios was influenced by local soil and climatic conditions. These results indicated that DRAINMOD-N II can be reliably used in the development and evaluation of drainage water and agronomic management practices that reduce N losses from drained agricultural lands.