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SCUAF
A Model to Estimate Soil Changes Under Agriculture, Agroforestry and Forestry

RUNNING the model

Running the model requires that Excel be available on the user's machine, as this software is used by SCUAF5 to handle data input and output. Despite this additional requirement, version 5 is a vast improvement on older versions, which were based on a laborious question-answer session under the DOS-operating system.

This version of the model takes advantage of the power and functionality of spreadsheets and makes the task of undertaking sensitivity analysis much easier than in older versions. Input files representing different agroforestry systems and/or different parameter values can be created in advance, on a spreadhseet that can be later read and analysed by SCUAF. Alternatively, the user can start from scratch, by creating a new input file using the default parameters provided by the model for a wide range of environmental conditions.

A typical session in SCUAF5 consists of the following steps:

1. Open SCUAF5 (click on the icon);

The window shown below will appear. This is the SCUAF Control Panel.

2. Click on "Set Defaults";

This will allow you to select the physical characteristics of the site where the agroforestry system will be established. For a description of these factors see the Defaults page:

Select your site characteristics and click OK. A new input file will be created and will be opened as an Excel spreadsheet. The soil and nutrient-cycle parameter values in this spreadsheet are based on the environment you selected. The plant-growth and management parameters are based on a simple agroforestry system, where 60 percent of the area is planted to a crop and 40 percent is planted to trees. This model is fully functional and it will run, but you should modify the relevant entries to represent your particular site (see how to edit input files).

After cklicking OK you will return to the SCUAF Control Panel.

3. Set the number of years to simulate

This is done by clicking the "years" box next to the "Run" button. A maximum of 100 years is allowed in this version of the model.

4. Click on "Run";

A new output file will be created and the outputs of the simulation will be written to this file.

Now you can move between the input file, the output file and SCUAF by clicking on the relevant window. A convenient way of arranging your windows is presented at the bottom of this page.

Subsequent runs will overwrite the contents of the output file. So, if you wish to keep these results copy them to a separate worksheet, either within the same output file or in a separate Excel file.

5. Modify the input file;

All model variables and parameters are available to the user through the input files. The user can change cut years, fertilizer applications, pruning, harvest etc.

The physical environment can also be changed by the user. This is conceptually equivalent to moving the agroforerstry system and management strategies to a different site. Default values supplied by SCUAF affect parameters related to organic-matter and nutrient processes in the soil and plant-growth parameters to match climate, soil fertility etc.

6. Return to step 4;

Continue the cycle 4-6 as long as desired. Each time the run button is pressed, SCUAF will: (i) read the input file (and pickup any changes you made in step 5), (ii) run the simulation for the required number of years, and (iii) write the results to the output file.


A convenient way of arranging your computer screen to run SCUAF is shown below. This allows simultaneous access to the input file and the output file as well as to the SCUAF program.


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