Module 5: Long-term simulations

IMPORTANT NOTE: It is highly recommended that you upgrade your APSIM Next Gen version to at least version 2023.2.7164.0 or later.

Long-term Simulations

Chickpea sowing rates - 40 year runs

In this exercise you will use sowing rules to plant Chickpea crops and observe yield probabilities for a 40 year period given a half full soil moisture profile at sowing. We will compare two sowing rate strategies for these conditions with the goal of maximising yield. The weather will be different each year but the soil starting conditions will be the same.

By default, in long term simulations (i.e. longer than one year), the end of one years' simulation becomes the starting point of the next year. This is useful if you are interested in seeing the degradation or improvement of the soil over a long time period. But what if you wanted to work out what the best strategy would be for the current year using weather scenarios from the past 40 years? To do this we could create 40 different simulations all with the same starting conditions but a different weather file (which would be a lot of work), or we could run the same simulation over 40 years and just reset the starting conditions each year (much simpler).

We can then try different management strategies to see which one would have worked best under the past 10 years weather scenarios.

  1. Start a new simulations using Wheat example.
  2. Rename the simulation as Chickpea and save the simulation as Module5.
  3. Change the Clock nodes' start and end date values to: 1/01/1940 and 31/12/1980
  4. Copy the Heavy clay soil from the Training toolbox and delete the exisiting Soil node.
  5. Set the starting Water to 50% full - filled from top.
  6. Set NO3 Depth to 0-1800 and initial value to 20kg/ha (right-click heading to change units).
  7. Set NH4 Depth to 0-1800 and initial value to 0kg/ha.
  8. Change the SurfaceOrganicMatter node's type to sorghum (don't forget to rename the pool name to sorghum as well), initial surface residue: 550 kg/ha, Carbon:Nitrogen ratio of 76, leave the Fraction of residue standing as is.
  9. Right-click Field and add a Chickpea plant node. All plants are found under the PMF folder.
  10. Delete Wheat.
  11. In Sow using a variable change the values to match the following: Sow using a variable's values
  12. Run the simulation.
  13. You should get an error that at it's end says: .Chickpea.Field.Report can not find the component: [Wheat]. This means we need to update the report variables and report events in Report. Let's change any that have [Wheat] to [Chickpea].
    • Remove [Chickpea].Grain.Protein.
    • Change the report variable [Wheat].Phenology.Zadok.Stage to [Chickpea].Phenology.Zadok.
    • Also, remember to change the report event down the bottom [Wheat].Harvesting.
  14. Run the simulation again.
  15. You should get an error with the message: Cannot find a soil crop parameterisation called ChickpeaSoil
    • This is caused by using a soil that is missing a SoilCrop node (located under Physical) with the same name as the plant node you are using. For now, create a copy of WheatSoil under Physical and rename it ChickpeaSoil to fix this exception.
  16. Before we run again, let's update our Harvest management node to look for the correct crop, now that Wheat has been removed and Chickpea has ben added.
  17. Your simulation should now run successfully and you should have data in your DataStore node. Datastore node
  18. Add a management script called Reset on date to the Chickpea simulation (found in Management Toolbox under Other) reset on date location
  19. Leave all parameters as yes and change the date to reset on to 1-may.
    • note: make sure this management script sits above all other management scripts in the tree as they are ran in the order they are arranged from top to bottom.
  20. Remove the Fertilise at sowing manager node.
  21. Rename the Chickpea simulation as Chickpea 10 plants.
  22. Copy Chickpea 10 plants and rename it Chickpea 15 plants.
  23. Change the Plant population(/m2) to 15 in the Sowing using a variable management script.
  24. Right-click the DataStore and click Empty the datastore. This makes sure that we have the most up to date data once we run, then run the simulations.
  25. Create a graph under Simulations. Rename it Total chickpea yield time series with a series that plots [Clock].Today and Yield.
  26. Now you have a graph showing yield when comparing differing plant density over 40 years.
    • If you've copied the graph settings from the image below and you can't see both simulations data displayed. Make sure Chickpea 15 plants sits above Chickpea 10 plants in the tree. Final total yield graph

Note: If you found any incorrect/outdated information in this tutorial. Please let us know on GitHub by submitting an issue.

Created 07/03/2023 - Last updated 05/03/2023