Modeling Nitrate Nitrogen Leaching in Response to Nitrogen Fertilizer Rate and Tile Drain Depth or Spacing for Southern Minnesota, USA
2000
Davis, D. M. | Gowda, P. H. | Mulla, D. J. | Randall, G. W.
The Agricultural Drainage and Pesticide Transport (ADAPT) simulation model was used to evaluate the relative effects of nitrogen application rate, tile-drain spacing, and tile-drain depth on NO₃-N losses through tile drains for conditions that are typical of the Upper Midwestern USA. The ADAPT model, a daily time-step continuous water table management model, was calibrated and validated for tile drainage and associated NO₃-N losses using long-term monitoring data measured on three experimental plots of a Webster clay loam (fine-loamy, mixed, superactive, mesic Typic Endoaquoll) under continuous corn (Zea mays L.) with conventional tillage treatment. For the calibration period, the model predicted mean monthly tile drainage and NO₃-N losses of 4.6 cm and 6.7 kg ha⁻¹, respectively, against measured tile drainage and NO₃-N losses of 4.6 cm and 6.9 kg ha⁻¹, respectively. For the validation period, the predicted mean monthly tile drainage and NO₃-N losses were 4.0 cm and 6.1 kg ha⁻¹, respectively, against measured tile drainage and NO₃-N losses of 3.7 cm and 6.5 kg ha⁻¹, respectively. Long-term simulations were made for a wide range of climatic conditions between 1915 and 1996 to evaluate the effect of drain spacing, drain depth, and N application rates on tile drainage and NO₃-N losses. Simulation results indicate that much greater reductions in NO₃-N losses occur with reduced N application rates than with increases in drain spacing or decreases in drain depth.
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