IMPORTANT NOTE: It is highly recommended that you upgrade your APSIM Next Gen version to at least version 2023.2.7164.0 or later.
APSIM simulates the influence of crop residues on the efficiency with which water is captured and retained during fallows. Residue cover declines as residues decompose. Residue decomposition is simulated in APSIM in response to weather, as well as the chemical composition of the residues. By doing this simulation you will reinforce skills learned in previous exercises and learn to do some basic editing of default values to “customise” your simulations.
This module assumes you have completed the previous module: “Module One: Fallow Simulation”. It will introduce you to the Surface Organic Matter module and demonstrate how surface residue decomposes over time.
For this module we will use the simulation we created in Exercise 1 (Module1) as a base. There is also a completed example in the training toolbox if you would prefer to use that. Open the file Module1.apsim.
Save the file as Module2.apsim in your
Apsim Training folder.
Remember to use
Save As not
Save or you will overwrite the old file.
Sand Fallow simulation. We’ll use
Clay Fallow as the starting point. Also delete the graph.
Make a copy of
Clay Fallow by dragging it to the simulations node in the tree and rename this new simulation to
Expand the new simulation then expand the paddock node. Click the SurfaceOrganicMatter module and change the initial surface residue to 3000 kg/ha.
Run both of the simulations, either by clicking on the
simulations node at the top and then clicking Run, or selecting them individually and running them.
Create a graph of Date vs surface organic matter cover (SurfaceOrganicMatter.Cover) and Weather.Rain (right hand axis) for the
Clay Residue simulation.
Clay Residue node.
Organic Matter Cover
Organic Matter Cover node,
Report as data source
line type to
marker type to
colour to yellow
Series node as
Create another series for rain under the
Organic Matter Cover node
on right? checkbox
Line type to
Marker type to
Colour to blue.
We will compare the effect that ground cover has on runoff.
Let’s build the graph
Let’s add another Series for
The APSIM residue model will decompose residues at differing rates according to the C:N ratio of the material. To demonstrate this we will reproduce the previous simulation but apply legume residues in the place of the wheat residues.
Clay Residue simulation. Rename it to
Clay Chickpea Residue. Remove the graph component.