The application of fertilisers to pastures in the high rainfall regions of southern Australia have contributed to large increases in carrying capacity since their introduction during the 1920s. Recently, large shifts in the world-wide demand for fertiliser inputs have lead to large rises in the cost of fertiliser inputs used at the farm level. The increasing cost of fertiliser inputs during a period of climatic uncertainty has significant potential ramifications on the future management of soil fertility and its interaction with the persistence and profitability of sown pastures. A dynamic pasture resource development simulation model was used to investigate the implications of fertiliser input cost on the optimal management of soil fertility under climatic uncertainty. The framework also allowed the investigation of how the management of soil fertility interacts with the utilisation of pasture resources through adjustments in stocking rates to maximise the expected present value of the grazing system. In the application of this method to the Cicerone Project farmlets case study, fertiliser input costs were found to influence the optimal combination of fertiliser inputs and stocking rate. The implications for grazing industries in the high rainfall regions of southern Australia are discussed.