The Tomato Calculator - A case study of developing decision support software for New Zealand's process tomato growers

The Tomato Calculator is a software Decision Support System (DSS) used to forecast fertilizer requirements of process tomato crops in New Zealand. It provides growers with a rapid and easily understood econometric analysis of how the available fertilizers are likely to perform. The DSS requires input data on planting date and soil chemical and physical conditions (from standard soil test procedures). The Tomato Calculator combines a model for potential yield with the PARJIB model for yield response to nutrient supply. Here we trace the development process from the first inklings of the model ideas through to industry deployment of the DSS. We concentrate upon how the ideas evolved, the influence that evolution had on the development of other DSS products, and the way in which the process challenged the ways that both the industry and scientists think about fertilizers, risks, and sustainability. The lessons learnt have important implications for other projects that involve developing DSS products for specific industry partners.