Nitrogen-Tillage-Residue Management: II. Calibration of Potential Rate of Nitrification by Model Simulation
1985
Clay, D. E. | Molina, J. A. E. | Clapp, C. E. | Linden, D. R.
NCSWAP is a computer simulation model of N and C cycles in the soil-water-plant system. It integrates water flow dynamics, N solute transport, crop growth, N transformations, and tillage, residue and soil temperature effects. Experimental data were obtained from a nitrogen, tillage and residue management field study conducted at Rosemount, MN. The objectives of this study were to calibrate the potential rate of nitrification and to illustrate how the model could be used as a research tool to infer behavioral characteristics of the soil-plant system. Significant differences in soil moisture, maize plant yield, and N uptake due to treatments were not detected either experimentally or by NCSWAP. A match between computed and observed tracer-N uptake and NO⁻₃-N and NH⁺₄-N in the surface (0-to 15-cm) soil depth was achieved when the potential rate of nitrification was set at 25 µg N g⁻¹ d⁻¹ at the beginning of the growing season, then reduced to 4 and 1 µg N g⁻¹ d⁻¹ from day 171 to 205 and from 206 on, respectively. NCSWAP showed that plant-N uptake drew from fertilizer-N during early plant development, but later from mineralized-N, which diluted the plant tracer-N content.
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