Economic modelling of controlled traffic in vegetable production

With very little experience of on-farm adoption of controlled traffic in the Tasmanian vegetable industry, it is not possible to conduct economic analyses of the costs and benefits of controlled traffic based on real life examples. There is considerable information about production costs for conventional vegetable cropping systems, and, improvements with controlled traffic have been reported for a range of industries and locations. Preliminary data from the Tasmanian vegetable industry agrees with the work of others, so estimates of changes to inputs and outputs of the vegetable production system can be used to model economic responses. A Microsoft Excel® based model was developed to predict how vegetable farm gross margins might change with use of controlled traffic. ModelRisk® (Vose Software) adds the capability to perform Monte Carlo simulations, allowing the impact of changing variables to be simulated many thousands of times. Gross margin worksheets for a range of common vegetable and green manure crops grown in Tasmania form the basis of the model. The impact of adopting seasonal controlled traffic farming (SCTF) or controlled traffic farming (CTF) is calculated by changing a number of variables through ranges that are expected to occur with adoption of either of these systems, and producing new gross margin calculations. Variables used include those likely to increase income or reduce expenses with the adoption of controlled traffic (e.g. – improved crop yield and quality, increased work rates, reduced fuel, irrigation and fertiliser use and tractor power), as well as those that could increase costs (e.g. – machinery modifications, guidance equipment and possible increased harvest cost). Outputs include cumulative probability curves showing the probability that SCTF and CTF gross margins will exceed the conventional gross margin, and tornado plots showing the sensitivity of the output to a range of inputs.