I have the following comments on Dr. Matthews' note on the use of models.

In South Africa (a developing country according to some definitions) there are examples of where models were applied as DSS or used as a basis for developing DSS.  Most of this has not been published in international journals.  Whether they were or are successful examples is also open to debate.  Recent examples are:

1. The PUTU model used for irrigation scheduling of many crops(De Jager ).  It is used mainly by consultants to provide advice to farmers.  An early version of the model is described by De Jager et al and a lot of work has been done since then to get it "user friendly".  Prof Jimmy de Jager ( [log in to unmask] ) would be in a better position to give you recent references.

2. The IRRICANE model (now called CANESIM and partly derived from the Canegro model present in the DSSAT package) is used for irrigation scheduling of sugarcane (Singels et.al 1997) and also as a general tool to assist agronomic management of sugarcane (Singels et. al. 1999).

In general my experience has been that you need to simplify models a lot to become successful DSS by reducing options (target for a specific use) and by creating friendly user interfaces (by professional programmers).  That is what we at SASEX are aiming to do at present.  We are working on a "friendly" Windows version of Canesim for general agronomic management and yield prediction, as well as stand alone, computerized "rule of thumbs" (or well established model principles, I suppose) to assist ratoon management, irrigation management, weed control and drying off. (See http://www.sugar.org.za/sasex/irricane/index.htm for an adapted example of Canesim)

We are not sure yet how we are going to get these applied by our 47 000 small scale farmers.  Interest from the commercial sector is high for irrigation scheduling (water is becoming expensive) and yield prediction (needed for optimal mill operation).

I don't fully agree with the idea that crop responses to decisions are relatively flat.  For example, sugarcane field research has shown huge responses to supplementary irrigation.  Changing climate as effected by crop scheduling also has quite a drastic effect on the crop.

Examples of models used in SA university education are:
1. When I was still with the Agrometeorology Dept, Free State University we used the PUTU suite of models for practical training of students in the crop modelling course.  Students generally struggled to master all the intricasies of the menus etc in the short time available, but my feeling was that they generally benefitted from the experience.  There were always a few bright sparks who would catch on quickly and realize the potential of models.  These lectures were in Afrikaans.
2. I am aware of the SWB model (John Annandale:  [log in to unmask] ) being used in courses presented at the University of Pretoria. You might want to contact him for further details.

I hope this helps.
Below are a few references.

De Jager, J.M., Van Zyl, W.H., Kelbe, B.E. and Singels, A., 1987.  Research on a weather service for scheduling the irrigation of winter wheat in the OFS.  Final report by the Department of Agrometeorology of the University of the Orange Free State to the Water Research Commission.  WRC Report No. 117/1/87. pp. 277.

Singels, A, Kennedy, AJ & Bezuidenhout, CN., 1998. IRRICANE: a simple computerized irrigation scheduling method for sugarcane. Proc S Afr Sug Technol Ass 72: 117-122

Singels, Kennedy & Bezuidenhout, 1999. Weather based decision support through the internet for agronomic management of sugarcane.  Proc S Afr Sug Technol Ass 73 (in press)



Abraham Singels
Agronomy Department, Experiment Station
S.A. Sugar Association
Private bag X02,
Mount Edgecombe 4300
South Africa

Tel: 031-5393205         Fax: 031-5395406
[log in to unmask]
www.sugar.org.za/sasex/about/agronomy.htm