Module 4: Sowing A Crop

Created 23/02/2023 - Last updated 05/03/2023

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

Sowing A Crop

In this exercise you will observe the growth of a crop over a single season. You will learn a bit more about how to use APSIM to do a ‘what-if’ experiment with fertiliser rates. These skills can not only be used to experiment with sowing fertiliser rates but also variables such as:

  • Time of planting.
  • Rate of sowing.
  • Crop comparisons and different starting soil moisture conditions.
  1. Start a new simulation using the Wheat.apsimx example. Open example simulation
    • you can find this in the open an example menu item
  2. Rename the simulation as Wheat.
  3. Save this simulation as Module4. Save the simulation
  4. Make sure that AU_Dalby.met is the selected met file under the weather node.
  5. Set the start and end dates of the simulation as 1/01/1989 - 31/12/1989 under the Clock node. Set dates
  6. Set the starting water to 25% full - filled from top. This is under Soil then Water. Set starting water
  7. Set the initial values column of both NO3 and NH4 to kg/ha. NO3 NH4
  8. Now let’s make some changes to the Fertilise at sowing management node.
  9. Change the Fertilise at sowing parameter Amount of fertiliser to be applied (kg/ha) to 0: SowingFertiliser to 0
  10. Let’s run the simulation and then inspect the Graph graph.
  11. Make sure the x and y axes are set to Clock.Today and Yield respectively.
  12. Rename the graph to Wheat Yield Time Series and its’ Series to Wheat Yield. Graph
  13. We can see with 0 sowing fertiliser we achieved a yield of almost 900 kg/ha.
  14. Next we will create an experiment where we alter the sowing fertiliser amount for this year. We will see how this affects the yield.

Creating an experiment

  1. First add a Experiment node to the Simulations node at the top of the simulations tree. Add an experiment
  2. The Experiment node will be added to the bottom of the tree, hold ctrl key and press up arrow several times until it is directly below the Simulations node.
  3. Add a Factors node to this experiment. Add a Factors node
  4. Add a Factor node to the Factors node. Add a Factor node
  5. To be able to change factors in our experiment, we will have to add our Wheat simulation to the experiment as a child node.
  6. Drag and drop the Wheat simulation node onto the Experiment node. Add wheat to experiment
  7. Delete the Wheat simulation that is not a child of the experiment node. Delete wheat
  8. Next, we will create several versions of our experiment with varying sowing fertiliser amounts.
  9. To do this, add this line to the Factor node: [Fertilise at sowing].Script.Amount = 0 to 60 step 30 Create experiment variations
  10. If we click back on the Experiment node, you can see 3 differing amounts of sowing fertiliser. See variations
  11. To see the results lets drag a copy of the Wheat Yield Time Series graph onto the Experiment node. Change the variables to reflect the image below: Setup graph
  12. Run the simulation. You’ll see that the sowing fertiliser amounts increase the yield of the wheat crop by varying degrees. Final graph

Congratulations on completing the 4th module

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