EPIC tile flow and nitrate loss predictions for three Minnesota cropping systems

Area of Science:

• Agricultural science
• Environmental modeling
• Soil science

Background:

• Subsurface tile drains are significant pathways for nitrate nitrogen (NO3-N) loss to streams in the north central USA.
• Accurate modeling of nitrogen (N) losses from agricultural systems is crucial for environmental protection and sustainable farming practices.

Purpose of the Study:

• To evaluate the performance of the Erosion Productivity Impact Calculator (EPIC) model in predicting tile flow and NO3-N loss.
• To assess the model's ability to simulate N fate under different crop rotations: continuous corn (CC), corn-soybean (CS), and continuous alfalfa (CA).

Main Methods:

• EPIC model simulations were compared against 4 years of measured data for tile flow, NO3-N loss, soil profile residual NO3-N, crop N uptake, and yield.
• Initial simulations used standard Soil Conservation Service (SCS) runoff curve numbers (CN2), followed by calibration of CN2 and a nitrogen parameter.

Main Results:

• Calibrated EPIC accurately tracked monthly tile flow and NO3-N losses for CC and CS rotations, though initial simulations underpredicted annual losses.
• Post-calibration, EPIC significantly improved predictions for CC and CS, with further refinement for CS NO3-N losses by adjusting a N parameter.
• The model showed poor performance for the CA simulation, despite replicating similar annual drainage volumes and N losses.

Conclusions:

• EPIC, after calibration, can effectively simulate tile flow and NO3-N losses for common row crop rotations in the region.
• Model performance for continuous alfalfa was inadequate, indicating a need for further development to represent diverse cropping systems accurately.
• The study confirmed EPIC's capability to reflect the relative impacts of different cropping systems on nitrogen dynamics.