Chickpea sowing rates - 10 year runs

In this exercise you will use sowing rules to plant Chickpea crops and observe yield probabilities for a 10 year period given a half soil moisture profile at sowing. You can compare two sowing rate strategies for these conditions.

By doing this simulation you will learn about rule based sowing, long term simulations, resetting soil moisture and nitrogen at sowing and graphing probability data.

The examples assume you have read and walked through the previous document: How to Build, Run and Graph a Simulation

  1. Start a fresh simulation using Continuous Wheat Simulation as a template
  2. Choose the Goondiwindi weather 1/01/1979 - 30/04/1989
  3. Select the "Black Vertosol (Garah No10011)" soil (Soils->Australia->New South Wales->North West Slopes and Plains) and rename it to Vertosol
  4. Set the Starting water to 50% full - filled from top.
  5. Set the Starting nitrogen to 20 kg/ha NO3 and 0 kg/ha NH4
  6. Change the surface residue type to sorghum (don't forget to rename the pool name to "sorghum" as well), initial surface residue: 550 kg/ha, C:N ration of 76, leave the Fraction of residue standing as is.
  7. Replace the wheat crop with chickpea.
  8. Replace the Sowing rule with the Sow using a variable rule from the toolbox.
  9. Set the properties of the sowing rule to:

    sowing window start date: 1-may
    sowing window end date: 1-aug
    must sow: no
    amount of rainfall: 15
    number of days of rainfall: 3
    amount of soil water: 200

    crop is chickpea
    sowing density plants/m2: 10
    sowing depth: 30
    variety: amethyst
    crop growth class: plant
    row spacing: 350

     

  10. Remove the sowing fertiliser rule.
  11. Make sure the harvesting rule will harvest chickpea, not wheat.
  12. Add the rule: Reset water, nitrogen and surfaceOM on fixed date. Use 1-may for the reset. Make sure the name of the soil module and the name of the surface organic matter module is correct (we renamed the soil to Vertosol). We want to reset water, nitrogen and surface organic matter to remove the year to year effects. (move it up to make sure it the first rule under Manager component. The order is important in the Manager Component. It is the order the rules are checked in)(right click on the rule and select "Move up")
  13. Choose these variables to report:
    Component Variable name
    Global year
    Chickpea yield
  14. Make sure the reporting frequency is set to harvesting.
  15. Rename simulation to Chickpea 10 plants
  16. Make a copy of the simulation and create a new one with 15 plants/m2
  17. Rename this copy to Chickpea 15 plants.
  18. Save the simulations as Sowing Rates.apsim
  19. Run simulations.
  20. Graph both output files creating a Year vs Yield by using a Graph component. Drag an "XY Chart" onto the Simulations node from the Graph toolbox. Change the X axis from "Date" to "year". Leave everything else as it is.
     

    21. Question 1: Why aren't there any bars in 1982?

  21. Create a probability of exceedance plot of Yield by using a Graph component. Drag a "Probability Exceedence" component onto the Simulations node from the Graph toolbox. It is that easy.