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Calibration Strategy for Nutrient Management in Land Use: Improving Nitrogen Loadings

This document outlines a calibration strategy aimed at improving the modeling of nitrogen (N) dynamics across different land uses, focusing on ammonia (NH3), nitrate (NO3), labile organic nitrogen (ORGN), and refractory organic nitrogen (ORGN). Key goals include ensuring end-of-field (EoF) loads are within target ranges, accurately simulating plant nitrogen uptake, and stabilizing nitrogen storage over time. The strategy involves optimizing parameters based on literature and observed data, refining decision rules for various land uses, and enhancing simulations of crop nutrient management practices to achieve more effective outcomes.

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Calibration Strategy for Nutrient Management in Land Use: Improving Nitrogen Loadings

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  1. Phase 5 Nutrient Land Calibration Jing Wu 04/04/2006 Modeling Subcommittee

  2. Calibration Targets – 8 for each land use NH3 NO3 Labile ORGN Refractory ORGN } SURFACE INTERFLOW (“slow” surface flow) lower soil layer NH3 NO3 Labile ORGN Refractory ORGN Groundwater

  3. Calibration Strategy • Decision rules developed to relate each target to relevant parameters - Parameters in the first two layers affected surface loading - Parameters in the 3rd and 4th layer affected below surface loading

  4. Status at last meeting: • Only two land uses tested • Most EoF targets not reached • Suggested changes on application data, EoF targets, and different decision rules

  5. Changes made since last meeting: • Application data (timing, plant uptake curve, etc..) • EoF targets TN remains same, changes in break-up between different species Surface: NH3/NO3 = 1:10 Subsurface: NH3/NO3 = 1:5 • Calibration strategy – decision rules different for different land uses - forest - crop, hay

  6. Forest Calibration • Targets changed based on literature values and P4.3 results TN = 1.7(lbs/acre/yr), same targets everywhere • Same decision rules as applied before

  7. Crop calibration Three goals need to be accomplished: 1.EoF loads within reasonable range of targets 2. Plant N uptake simulated correctly, within reasonable range of observed data (critical, account for most of N loss) 3. Stable N storage over time

  8. Calibration Strategy • Optimize parameters as did for Forest - to reach EoF targets • Optimize initial storages for labile and refractory organic nitrogen - to eliminate huge spike at the first year due to high initial storage - to stabilize storage over time

  9. Related initial storage to organic N export at the first three years

  10. Calibration Strategy (cont.) • Improve simulation on crop uptake - Change the timing of application data - Return 60% plant N to refractory organic N . act as a way to harvest plant (will increase refractory organic N export, though)

  11. Old data Application timing closer to uptake After fixed storage and plant N return

  12. Percent of each crop 8% 42% 50%

  13. High till with manure

  14. High till without manure

  15. Low till with manure

  16. Comparison of regular crop and nutrient management crop • Test model’s capacity of simulating management actions • Use the calibrated land parameters to run nutrient management land • TN and plant uptake compared

  17. Comparison of hom and nho On average, 32% lower On average, 11% lower

  18. Preliminary observations: • New results promising • Majority of EoF loadings within reasonable range of targets • Plant N uptake within the range of observed data • Further refinement needed

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