A model and its implications for denitrification in soil environment

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• The Crop-Environment Resources Synthesis (CERES)-maize model simulates crop yield and includes a soil nitrogen (N) sub-model.
• Understanding N transformations, particularly denitrification, is crucial for managing N losses in agricultural soils and addressing human impacts on the N cycle.

Purpose of the Study:

• To analyze the mechanisms of the CERES-maize soil N sub-model.
• To assess the impact of various parameters and organic matter treatments on N transformations, focusing on denitrification.
• To identify the dominant factors influencing N losses in upland soils.

Main Methods:

• Calibrated and validated the CERES-maize model in Taiwan.
• Conducted specific experiments to test the N sub-model's performance against field observations.
• Developed computer programs to calculate parameter sensitivity and simulate organic matter treatments.

Main Results:

• Soil water content and temperature were identified as the most dominant factors influencing N transformations, significantly more so than decomposition rates, soil pH, or bulk density.
• Fractional treatment of organic matter with varying carbon/nitrogen (C/N) ratios slowed decomposition.
• Fractional organic matter treatment decreased denitrification, except when the organic matter quantity was very large with a high C/N ratio.

Conclusions:

• Soil water content and temperature are critical drivers of nitrogen cycling and loss through denitrification.
• Managing organic matter decomposition through fractional application can mitigate nitrogen losses and reduce denitrification.
• The CERES-maize N sub-model effectively simulates field observations, providing a tool for understanding and managing soil nitrogen dynamics.