Rotations

Creating a wheat long fallow rotation

In this exercise, you will create a wheat long fallow rotation where wheat is potentially sown every second year.

  1. Create a new simulation based on Rotation Sample
  2. Change the name of the simulation to LongFallowV and save to the same filename.
  3. SaveAs LongFallowV.apsim
  4. Check met file is Goondiwindi 1940-1989 and make the simulation run for entire length of met file (1/01/1940 to 31/12/1989).
  5. Change the soil to "Black Vertosol-Waco (Jimbour No016)". (Soils->Australia->Queensland->Darling Downs)(remember to rename it)
  6. Delete the cotton and chickpea crops from the simulation. (we will only be doing wheat and summer and winter fallows in this simulation)
  7. Delete all the sowing rules and harvesting rules for every crop other than Wheat
  8. Change minimum allowable soil water criteria of the Wheat sowing rule to 0 so that it doesn't play a part in the sowing criteria.

  9. Set the crop order in the Rotations rule to the following:

    1st crop wheat
    2nd crop sf
    3rd crop wf
    4th crop nil

    (set 5th and 6th crop to nil as well. Just so you don't get confused later)

    sf, wf and nil are standard abbreviations. sf for summer fallow, wf for winter fallow and nil for the point where the rotation will return to the beginning and repeat. APSIM will not recognise anything else.

  10. Reorder the rules in the Manager component so that Rotations rule comes first followed by the sowing rules then the harvest rule
  11. Choose these variables to report:

    Component Variable name
    Global Date (dd/mm/yyyy)
    year
    Wheat yield

  12. Change the output frequency to harvesting.
  13. Run APSIM and plot year vs yield using a graph component.

Fixed vs variable rotation

  1. Duplicate the previous simulation and name it LongFallowF
  2. Change the wheat sowing rules in the LongFallowF simulation from
    must sow = No to Must sow = Yes
  3. Run this second simulation and plot year vs yield for both simulations on the same graph using a graph component

    What are the differences between fixed and variable ?

Off-Setting the Rotations

  1. Duplicate the LongFallowF simulation and name the new one LongFallow0
  2. Set the crop order in the Rotations rule to the following:

    1st crop wf
    2nd crop sf
    3rd crop wheat
    4th crop nil

  3. Run this simulation.
  4. Plot year vs yield for both LongFallowF and LongFallowO on the same graph using a graph component. To do this, do it as if you were going to plot all the simulations on the one graph. When you view the graph of all three simulations you will notice some checkboxes below the graph. One for each of the simulations. Just untick the LongFallowV

    If you worked out the average yield for LongFallowF and worked out the average yield for LongFallowO, would they necissarily be the same ?

Wheat sorghum rotation

  1. Rename LongfallowF simulation to SorghumWheat Rotation, remove other simulations and save to a new file called SorghumWheat.apsim. (remember to use Save as button. Not Save)
  2. Add Sorghum crop from the toolbox.
  3. Add Sorghum sowing rule from the toolbox, rename to SorghumSowing. Set cultivar to early and must sow to yes.
  4. Rename Fertilise at sowing rule to WheatFertilise. Copy it, and rename the copy SorghumFertilise (make sure to change the "On which module should the event come from" property to sorghum).
  5. Add a Harvest Rule from the toolbox, rename to SorghumHarvesting and change crop from wheat to sorghum.
  6. Make sure the sowing windows for sorghum and wheat sowing rules match those in the table above.

  7. Set Rotation sequence to sf, wf, sorghum, wf, sf, wheat, nil.

  8. Add the following variables to your simulation:

  9. Run simulation and plot year vs WheatYield and SorghumYield using a graph component.

Sorghum Wheat Chickpea rotation (advanced)

In this exercise, you will create a sorghum wheat chickpea rotation that looks like the above diagram without step by step instructions. Use the previous wheat / sorghum rotation as a starting point.

Use these default sowing properties for wheat, sorghum and chickpea:

must sow = no, minimum soil water = 0, cultivar for chickpea is "amethyst", default everything else.