Crop modeling in Namibia

Abstract

In the last decade, in a dry African country like Namibia it became important for the Ministry of Agriculture, Water and Rural Development to compile a computerized inventory of the country’s natural resources to assist planners, managers and researchers in the attempt to increase food security. This need gave birth to the Agro-Ecological Zoning of Namibia programme.

The latest crop modeling and crop management responses technology called, “Decision Support System for Agrotechnology Transfer “ (DSSAT)” arrived in Namibia in June 1999. The advantages of the DSSAT system, which can model the growth of seventeen crops, are the standardized inputs (soil and climate) and a strong analyzing component. Once DSSAT has been validated for Namibia with historical and future data, suitability and economic simulations can be run on computer.

However DSSAT and its initiators (the Agro-Ecological Zoning programme) needed to overcome some challenges. In Namibia crop research was still done in the traditional way. Traditional means an empirical approach and shortcomings in extrapolation to real-life situations. Other problems were unpublished data, a need for a minimum set of historical data and a serious shortage of model minded people and the always present money problem.

The challenge was met with the following work plan. Demonstrations of the DSSAT models were held. Data needs to calculate the genetic coefficients for the cultivars used were specified and it was clearly indicated that initially small and low impact changes to the researchers current and future trials were necessary to do this validation. Researchers were visited one by one to unearth all possible research results for testing the models. This personal approach assisted us in changing his or her mind on the usefulness of the modeling approach, especially by using the analyses available in the DSSAT system and the need for him or her because of their practical experience to assist us in the testing of the models. This helped enormously in changing the outlook of the researchers and extension staff of the Ministry to the usefulness of modeling in understanding the performance of crops. The next step was to coordinate the planning of the 2000/2001 season’s experiments so that more appropriated data could be generated for model testing. Training was provided for research and extension staff to use and develop the DSSAT system themselves and make it part of a new tradition in the Ministry. Researchers were encouraged to start with the model applications they felt most confident with and then continue testing the models for further applications. Finally, for some of the crops/cultivars the genetic coefficients had been acquired from our South African colleagues who have done some good work during the last decade and these could be used for initial analyses.