Did you notice that your COMET Planner practice “Improved N Fertilizer Management…Reduce Fertilizer Application Rate by 15%” shows an increase in total emissions?
There is assumption in the modeling that the baseline involves an over-fertilization and the CPS590 would improve overall efficiency, reducing the application rate. However, the only data we have on nitrogen rates is from USDA ERS that gives average nitrogen rates by crop. We are uncertain if this is an over-fertilization or not; therefore, we might actually be reducing too much. To read further about the COMET-Planner modeling in relation to this practice, please refer to page 19 in the COMET-Planner report. One page summaries are available for each practice when users select the "i" button to the left of a practice in Step 4.
The model is sensitive to nitrogen availability, especially in the case that the amount does not exceed other ecosystem controls on productivity. In other words, if there is sufficient sunlight, water and PK, the plant growth would match the nitrogen availability, and if only nitrogen availability is reduced, plant production decreases. The reductions in productivity reduces carbon inputs to the system. You’ll see that N2O rate goes down, but CO2 emissions increase. In theory, using CPS590 should not reduce productivity/yields. Because of this, COMET-Planner no longer (as of Sept 2022 updates) provides a CO2 or soil carbon emission/reduction estimate.