A sorghum crop simulation

Exercise 4: A sorghum crop simulation

Response of crop to N fertiliser

In this exercise you will observe the growth a crop over a single season.

You will learn a bit more about specifying a Manager template, execute more than one run in batch mode and use the simulator to do a “what-if” experiment with fertiliser rates. These skills can also be used to “experiment” with time of planting, rate of sowing, crop comparisons and different starting soil moisture conditions.

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 Sorghum Simulation as a template
2. Rename the simulation as Sorghum Nil Fertiliser. Save the filename as Sorghum Fertiliser.apsim
3. Choose the Dalby weather 1/1/1988 - 30/6/1988
4. Select the Black Vertosol-Mywybilla (Bongeen No001) Soil. (Soils->Australia->Queensland->Darling Downs)(remember to rename it)
5. Set the Starting water to 25% full - filled from top.
6. Set the Starting nitrogen to 12 kg/ha of NO₃ and 3 kg/ha of NH₄, evenly distributed.
7. Change the sowing rule to:

   set sowing date to 1-Jan by setting both the ‘window start’ and ‘window end’ to 1-Jan and ‘Must Sow’ to ‘yes’.
   set sowing density to 8
   set sowing depth (mm) to 30
   set cultivar to early
   set row spacing to 1000mm
   skip row to solid
   leave all the other parameters as they are.

8. Check that the harvest rule indicates that Sorghum should be harvested.
9. Remove the Sowing fertiliser rule from the Manager component.



10. Choose these variables to report:

    Component	Variable name
    	dd/mm/yyyy as Date
    Clock	Day
    	Year
    Soil (whatever you renamed it to)	Depth - layered (mm)
    	Soil water - layered (mm/mm) (sw)
    Sorghum	DaysAfterSowing
    	LAI
    	Biomass
    	Yield

11. Choose a end_day reporting frequency.
12. Make a copy of the simulation by dragging Sorghum Nil Fertiliser node to the Simulations node at the top of the simulation tree.
13. Rename this copy to Sorghum 30 kg N Fertiliser.
14. Add a Fertilise at sowing rule to the Manager folder component. Apply 30 kg urea_n fertiliser, making sure to change the "On which module should the event come from" name from wheat to sorghum.
15. Make another copy of the simulation, this time adding 60 kg/ha of fertiliser. Call the simulation Sorghum 60Kg N Fertiliser
16. Run all 3 simulations.
17. Graph all 3 output files creating a Date vs Yield chart using a graph component. Click on the Graph toolbox. Drag an XY Chart onto the top node Simulations.

Rate of water extraction from soil profile

Create a new depth chart of dlayer vs sw with 2 dates 15 Mar (crop is growing) and 31st May (after the harvest).

Drag a Depth component onto the top Simulations node. Expand the Plot node to get the Depth node. Tick the dates mentioned above. In the Plot node, add "sw" as the X variable and leave the Y variable as "Depth"