Getting started

Even the smallest farming systems are a complex interaction of resources, tasks, processes and management decisions. Before you build a CLEM simulation for the system you wish to model it is worth taking some time to develop a clear picture of what is needed. Try following the steps below to get started.

CLEM is provided as a stand-alone model within the Agricultural Systems Modelling and Simulation (APSIM) software (Next Generation version). You will not require any previous understanding of APSIM or the use of any APSIM crop models to use CLEM. To start using CLEM you will need to follow the instructions to register as an APSIM user and download and install the software. APSIM Next generation is available for Windows, MacOS and Linux based systems.

More information about APSIM

Download here (ensure you select APSIM Next Generation)

  1. Select Commercial or Non-Commercial use image
  2. Click Downloads under How to register and download APSIM
  3. Select APSIM Registration system for new users or APSIM Upgrade page
  4. Select APSIM from Product and Next Generation (your operating system) from Version drop down boxes
  5. Complete registration information and click Yes I agree, begin Download
  6. Install APSIM when the file is downloaded.

By default APSIM will install into a system directory (e.g. c:\Program Files on Windows computers). Installing to this path requires administrator rights. As this elevated level of access is not commonly granted to all users in an organisation, we recommend that you install APSIM to a local folder on your main drive (not a network path) with your usual login. This will allow you to install and upgrade APSIM Next Generation without needing administrator rights and IT support (note: always check with your company software policy before installing new software).

The APSIM Next Generation installation includes a number of CLEM examples to help you get started.

Think of all the resources in the farm that need to be modelled. This will include both the products produced and the things needed to produce them such as land, finances and labour. The level of detail required from your simulation will also determine which resources you need to include in the simulation. For example you may not wish to include the financial calculation when considering herd growth rates using different feeding strategies.

Think of all the tasks (or activities) that need to be performed. This will help you prepare the model. Tasks may be critical things to do like grow a crop, but also all the smaller tasks that are involved such as purchase seed, pay a particular bill, or move animals. You will quickly realise that there can be a large number of activities needed.

The next step is to become familiar with using the APSIM Next generation user interface and how a CLEM model is put together. The Using CLEM section will take you through this process step by step.

As you start building your simulation by adding components to the simulation tree you will need to provide parameter values that allow the simulation to represent your particular system. Most of these will seem logical and are easy to define. Other parameters, such as those needed to describe how a particular ruminant type behaves, are more difficult and require expert input. Fortunately, others may have already parametrised these components for you to add to your simulation and you can add them from toolboxes and example simulations if available to you. CLEM also relies on other models, existing data or even expert opinion to provide information such as crop and pasture growth and the timing and amounts harvested. You will need to provide external data files to supply this information (see Data readers).

Even experts can get the setup of the simulation wrong. CLEM offers a range of methods to let you know what went wrong and help you get your simulation working. See Summary information for details.

After a simulation has been successfully performed, you will need to display the results to understand what happened. See Reporting and graphing model output for more details.

The last step involves modifying the simulation to explore how changes to management affect the outcomes of the simulation. You can duplicate simulations in your simulation tree to run them side by side with all results recorded in the output database. Also, by changing the order in which tasks are performed you can change their priority (see Importance of component order) and explore the outcomes. APSIM Next Generation also provides functionality to run experiments where a variable is altered between each simulation. This is useful for parameter sensitivity and scenario testing .

See next section - The user interface