Easier description of inert OC in SoilN2

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Legacy Bug ID: 1026 Author: Neil Neil Huth Date: 2009-09-04 09:38:45 +0000 UTC

"FInertThe soiln2 parameter FInert has confused people for some time now.  We have spoken of ways in which we can help people back-calculate what it's value should be.(new line);(new line);On reflection, it would appear that perhaps an equivalent parameter InertC (or some other name) with the same units as OC (i.e.%) would make more sense.  In some ways, this parameter can be measured.  If not, it can more readily be understood and estimated by the user.Version: Found By:Neil HuthContact:neil.huth@csiro.au"

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Author: sno036 Date: 2009-09-03 11:46:00 +0000 UTC

APSoil and SoilN2 have been set up using the assumption that there is no N in the inert pool.  This has been appropriate for the cropping regions of Australia and other warmer climates where most of the inert material is charcoal but in temperate soils there are significant amounts of organic nitrogen in the inert component of the soil organic matter.  For example a typical NZ grassland soil might have 5% org-C in the top few cm but about 3% would be inert with a C:N ratio of about 10 so the inert org-N would be about 0.3%.

At present we are dealing with this by excluding all the inert C and N from the simulation (lying about the total C and N in the soil!) and setting “FInert” to 0.  While this is functional it is not a good permanent solution.

Finding a better solution will require some thought (so as not to disrupt the current work that has gone into APSoil) but will have implications for both SoilN2 and the UI.  However the timing to think about this is probably about right (more usage in temperate grasslands and currently considering how APSoil might serve SWIM) so I’d like to start this discussion soon if possible.

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Author: hut104 Date: 2009-09-04 09:38:00 +0000 UTC

The parameter Finert has confused users for quite some time with many people even trying to ignore it.  Changing the parameter to an amount (% as per OC) will allow users to apply the rules of thumb for its determination (as per guilelines by Merv Probert) or enter measured values.  Measured estimates are becoming more common as Carbon accounting becomes a bigger issue.  This will make apsim much more useable

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Author: sno036 Date: 2009-09-07 10:48:00 +0000 UTC

And if users also put in a %OrgN for the inert pool this would address my issue as well - need to add in an inert-N pool inot SoilN2 = see BugID 1022.

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Author: devoil Date: 2009-10-06 09:38:00 +0000 UTC

merged bug 1022 into this bug:Organic nitrogen in the inert pool - affects UI, APSoil, and SOilN2

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Author: devoil Date: 2009-10-06 10:32:00 +0000 UTC

merged bug 278 into this bug:"FInert"

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Author: hol353 Date: 2009-11-27 09:49:00 +0000 UTC

Reference Panel Recommendation: Enli Wang reviewer. Neil Huth and Val Snow to combine this proposal with "1026: Easier description of inert OC" submitted by Neil Huth.

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Author: enli.wang@csiro.au, Date: 2010-08-06 14:58:00 +0000 UTC

Subject: APSIM Modification: Easier description of inert OC in SoilN2 (DO NOT EDIT THIS:1026) Dear Enli,

The APSIM Initiative Reference Panel has received a proposal to modify APSIM titled "Easier description of inert OC in SoilN2".

Given your field of scientific expertise, the Reference Panel believes that you would be an appropriate Technical Reviewer of this modification. 

If you can confirm that you are able to undertake this review it would be greatly appreciated.

The following is a link to the Task with  relevant supporting documentation (scroll down the page for updates):

http://www.apsim.info/BugTracker/edit_bug.aspx?id=1026

I look forward to hearing from you.

Regards

Chris Murphy 
Principal Project Officer (APSIM)
Agri-science Queensland
Department of Employment, Economic Development & Innovation 
203 Tor Street, Toowoomba, Queensland 4350, Australia
PO Box 102, Toowoomba, Queensland 4350, Australia
t: +61 7 4688 1596 
f: +61 7 4688 1193 
e: apsim@dpi.qld.gov.au 
w: www.dpi.qld.gov.au 

The APSIM (Agricultural Production systems siMulator) Initiative is an unincorporated joint 
venture between the Commonwealth Scientific and Industrial Research Organisation, 
the State of Queensland and The University of Queensland. 
Website www.apsim.info

[ApsimBot]

Author: murphy Date: 2010-12-02 15:06:00 +0000 UTC

Reminder sent to Enli on 2 December 2010.

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Author: guest Date: 2010-12-10 09:14:00 +0000 UTC

I think we need to separate the inert carbon (C) from the humic pool (HUM) by adding an extra pool. It can be called either inert organic C (IOC) or resistant organic C (ROC). This would enable us to easily accommodate the concept of measurable pools and to initialise the carbon pools in our model with measurements in the future. A C/N ratio for this pool can also be assigned.

             

            For people who only have measurement on total organic carbon (TOC), we still need to have some rules of thumb in the model to facilitate the initialisation of the pools. This can be implemented in the user interface with clear description of how each pool is estimated based on the TOC and rules of thumb.

         

        In addition, we need to think further about future development of SoilN (or may be called SoilCN). Particulate Organic Cabin (POC) is being measured as one measurable fraction of the total organic carbon (TOC). My understanding is that POC is the finer fragments (53um~2mm, and sorbed molecules) and a result of Fresh Organic Matter (FOM) decomposition (or just breaking down). We need to think whether we need to add a POC pool, or we use one of the FOM sub-pools for POC. Either way, POC needs to be linked to the rest of FOM and needs to be decomposed into BIOM and HUM. If POC is just a by-product of FOM decomposition, i.e., the fraction that is harder to decompose or not yet broken down, the process of deriving POC per se may not be a decomposition, i.e., not producing CO2 and release N.   

         

        A further question is whether we still separate the FOM-POC into the three sub-pools in the same way as we have now, and another related issue is the need of separate C/N ratios for each of the FOM sub-pools.

[ApsimBot]

Author: murphy Date: 2011-02-03 10:13:00 +0000 UTC

Review Comments from Enli Wang below:

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Author: hut104 Date: 2011-02-03 10:41:00 +0000 UTC

For the sake of clarification for the reference panel let me add a summary of what I see as the way forward.  I'll also clarify a few misconceptions from below.

Currently, the soil OM consists of FOM(with 3 sub pools), BIOM, HUM and INERT.  The soil OC% that is specified in the parameter set is divided into the HUM and INERT pools using the parameter Finert.  Both these pools (HUM,INERT) are said to have the same C:N, which is also a parameter.

Methods are being undertaken, and have been tested with APSIM, for measuring the INERT pool.  For this reason it was originally suggested that we convert the parameter Finert into a new parameter of the same units as OC% as this reflects what is measured.  This will also cause less confusion, and easier parameterisation for users as Finert is currently linked to the value of OC.  (You should not change one without changing the other.)  When the new parameter is added, we should add a new specification for the INERT pool C:N.  This can default to the soil C:N, currently provided by the user, as this would provide full backward compatibility in all simulations.  The Soil HUM C:N can then be calculated from the data already provided thus simplifying things for the user.

The questions regarding the number and meaning of the FOM pools can be evaluated in the short to medium term without changes to the model structure.  We already provide to users configurations of SoilN that represent the standard pool configuration, and the RothC configuration.  I'd suggest leaving any changes here to wait for extensive testing as any changes here will have far ranging impacts on issues such as decomposition of different plant litter types in mixed farming systems through to manure decomposition rates in Africa.  The impacts of pool structure on P dynamics would therefore need to be considered.

I'd recommend implementation of the original suggested changes in the near future as it will provide great benefit to users in a range of projects.  The suggested changes do not require extensive coding.

[ApsimBot]

Author: murphy Date: 2011-02-17 10:12:00 +0000 UTC

The Reference Panel at its meeting of 04/02/11 noted the review comments from Enli Wang and clarification from Neil Huth. 

 

ACTION:

RP recommendation is to proceed with implementation as per the original proposal.

[ApsimBot]

Author: ver078 Date: 2012-01-17 16:24:00 +0000 UTC

Reviewer: Enli Wang

Review Panel Contact: 
Dean Holzworth