An overview of APSIM, a model designed for farming systems simulation

TLDR: The paper outlines APSIM's structure and provides details of the concepts behind the different plant, soil and management modules, including a diverse range of crops, pastures and trees, soil processes including water balance, N and P transformations, soil pH, erosion and a full range of management controls.

About: This article is published in European Journal of Agronomy.The article was published on 2003-01-01 and is currently open access. It has received 2431 citations till now.

Figures

Fig. 2 (Continued)

Fig. 1. Diagrammatic representation of the APSIM simulation framework with individual crop and soil modules, module interfaces and the simulation engine.

Fig. 2 (Continued)

Table 2 A subset of the reports on APSIM testing

Table 1 Current crop modules in APSIM and relevant references

Table 3 Summary of reports of APSIM application over the 1996 /2001 period

Frequently asked questions

Q1. What have the authors contributed in "An overview of apsim, a model designed for farming systems simulation" ?

The paper outlines APSIM ’ s structure and provides details of the concepts behind the different plant, soil and management modules. 

Q2. What is the rate of decomposition of the various soil organic matter pools?

Any release of N during the decomposition process in excess of the immobilization demand results in an increase in the ammonium-N.The rates of decomposition of the various soil organic matter pools are dependent on soil temperature and soil water content of the layers where decomposition is occurring. 

Q3. What is the ability to simulate processes using different simulation approaches?

The ability to simulate processes using different simulation approaches is met using switches that are specified in the crop parameter file. 

Q4. What are the key reports that compare APSIM predictions with observed data?

Because APSIM was intended to be a model that could be applied to complex farming systems issues, the reports that compare model predictions with farming system performance over long-term crop/forage rotations are particularly important (e.g. Probert et al., 1995; Jones et al. 

Q5. What is the role of APSIM in agriculture?

Simulating multi-species mixtures will find increasing application as APSIM is applied to more complex issues in farming systems. 

Q6. What are the useful model evaluation reports?

The most useful model evaluation reports are those that have examined predicted and observed values of a range of plant and soil state variables over an extended period. 

Q7. What is the definition of a crop template?

Such a template, often referred to as a ‘crop template’ but potentially applicable beyond just crops, provides a means to capture unifying principles, testing new insights, and comparing approaches to component modelling, while maintaining a focus on predictive capability. 

Q8. What is the ability to detain surface water?

This capability to detain surface water can change through time, e.g. increasing as a result of cultivation, or decreasing due to the impact of raindrops. 

Q9. What are the challenges in incorporating P constraints into crop growth models?

The crop modules have also required modification; P uptake needs to be simulated and P stress in the plant calculated so that crop growth is constrained under P limiting conditions. 

Q10. What is the composition of the surface residue pool?

Crop residues are added to a single surface residue pool that is described in terms of its mass, the cover it provides for the soil surface, and its nitrogen content. 

Q11. What is the effect of the formation of biom and HUM on the soil organic matter pool?

The formation of BIOM and HUM thus creates an immobilization demand that has to be met from the N released from the decomposing pools and/or by drawing on the mineral N (ammonium and nitrate) in the layer. 

Q12. What is the ability to switch between modules?

The ability to switch between optional processes within sub-modules or between optional entire sub-modules facilitates logical comparative analysis of modelling approaches. 

Q13. What is the effect of removal of residues on the soil organic matter pool?

The amount of residue may decrease due to: (1) Removal of residue (e.g. by burning or baling); such action does not alter the C:N ratio of the residues.