The Design Document page provides a description of the algorithms, implementation and planned testing including unit, verification, validation and performance testing. Please read Step 1.3 Performance Expectations that explains feature documentation requirements from the performance group point of view.
Design Document
In the table below 4.Equ means Equations and Algorithms, 5.Ver means Verification, 6.Perf - Performance, 7. Val - Validation, 
- competed, 
- in progress, 
- not done
Overview table for the owner and an approver of this feature
1.Description | Flow of Agricultural Nitrogen |
| 2.Owner | Beth Drewniak |
| 3.Created | |
| 4.Equ | |
| 5.Ver | |
| 6.Perf | |
| 7.Val | |
| 8.Approver | |
| 9.Approved Date |
Title: bbye/lnd/fertilizer: Flow of Agriculture Nitrogen
Requirements and Design
E3SM Land Group
Date:
Summary
The purpose of this code is to add NH3 emissions from fertilizer and livestock waste under different environmental conditions. Volatilization of ammonia is a major pathway of nutrient loss in ecosystems and is the largest emission source of atmospheric NH3. Atmospheric emission, transport, and deposition of NH3 is an important component of the nitrogen cycle, and is sensitive to environmental conditions which are not captured with static emission inventories. This code includes volatilization of NH3 from both livestock manure and synthetic fertilizer as documented in Riddick et al. (2016) and Vira et al. (2020). I will include some of the major requirements in the following design documentation, but details can be found in the published manuscripts linked. There are several modes that FAN can operate with: fan_on (emission calculation only), fan_soil (fan coupled to the soil biogeochemistry), fan_atm (fan coupled to the atmosphere only) and fan_full (coupled to both atmosphere and soil). Of these modes, only fan_on and fan_atm will be scientifically validated as fan_soil and fan_full do not have nitrogen balance checks between ELM and FAN (the N is balanced within FAN and ELM independently).
This code also includes updates to the cropland fertilizer subroutines. Modifications include a gridded synthetic fertilizer dataset of both nitrogen and phosphorous for each crop type, as opposed to the current fixed rates of nitrogen only. These changes are incorporated into the surface dataset and include modifications to the mksurfdat tool for generating surface input data. The fixed fertilizer rate that was used previously will be converted to a manure input, which will be replaced by the FAN stream data when FAN is on.
Requirements
Requirement: name-of-requirement-here
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Each requirement is to be listed under a ”section” heading, as there will be a one-to-one correspondence between requirements, design, proposed implementation and testing. Requirements should not discuss technical software issues, but rather focus on model capability. To the extent possible, requirements should be relatively independent of each other, thus allowing a clean design solution, implementation and testing plan.
Algorithmic Formulations
Design solution: short-description-of-proposed-solution-here
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For each requirement, there is a design solution that is intended to meet that requirement. Design solutions can include detailed technical discussions of PDEs, algorithms, solvers and similar, as well as technical discussion of performance issues. In general, this section should steer away from a detailed discussion of low-level software issues such as variable declarations, interfaces and sequencing.
Design and Implementation
Implementation: short-desciption-of-implementation-here
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This section should detail the plan for implementing the design solution for requirement XXX. In general, this section is software-centric with a focus on software implementation. Pseudo code is appropriate in this section. Links to actual source code are appropriate. Project management items, such as svn branches, timelines and staffing are also appropriate. How do we typeset pseudo code?
Planned Verification and Unit Testing
Verification and Unit Testing: short-desciption-of-testing-here
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How will XXX be tested? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?
Planned Validation Testing
Validation Testing: short-desciption-of-testing-here
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How will XXX be tested? What observational or other dataset will be used? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?
Planned Performance Testing
Performance Testing: short-desciption-of-testing-here
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How will XXX be tested? i.e. how will be we know when we have met requirement XXX. Will these unit tests be included in the ongoing going forward?