Improving Crop Growth Simulation in the Hydrologic Model DRAINMOD to Simulate Corn Yields in Subsurface Drained Landscapes

The primary goal of drainage research has been shifting from maximizing crop production to environmental impacts with the increasing concern related to the transport of nutrients, specifically nitrate-nitrogen (NO3-N) with subsurface drainage water from agricultural lands. It is becoming important to evaluate the impact of drainage design and its management not only on crop production but also on nutrients, primarily nitrogen transformation and transport from agricultural lands. The hydrologic models DRAINMOD and DRAINMOD-NII simulate subsurface drainage design and management, and its impact on N-transformation and transport from artificially drained soils. However, both models use a simplified yield reduction approach to simulate the crop growth, its production and impact on hydrology and nutrient dynamics of subsurface drainage landscapes. The objective of this study, therefore, was to integrate a deterministic crop model CERES Maize into DRAINMOD as an option for the simulation of detailed corn growth and development accounting for weather and soil water dynamics in field conditions. The integrated DRAINMOD and CERES Maize model was evaluated by comparing the simulations with observations from three (Readlyn; Kenyon and Floyd) soil plots located at the Iowa State University Northeast Research Center, Nashua (IA). The preliminary model results are encouraging showing a good correspondence with the observed soil water content, subsurface drainage and crop yields during the years from 1990 to 1992. The integration of detailed crop models into DRAINMOD would capitalize on their strengths, and enhance the capability of modelling the subsurface drainage systems