Farm and catchment scale effects of managing dry-land salinity with pastoral and woody perennials

Dry land salinisation is a significant cause of land and water degradation in Australia. Changing land use from annual to perennial crops has been widely proposed as a means to reduce land degradation and increase the productivity of saline land. However, in many areas annual crops are financially more attractive than perennial crops. Increases in perennial crops might also reduce local stream flows with adverse effects on in-stream values. As such salinity control is likely to involve significant tradeoffs between public and private costs and benefits. This paper considers the impact of planting differing areas of pastoral and woody perennials on farm profitability (P), and water (W) and salt (S) exports from the Little River catchment in New South Wales (NSW), Australia. The analysis uses two linear programming (LP) models. The first model represents a mixed crop and sheep system and the outputs of this model are integrated to provide inputs to a second catchment level model. The structure of the LP models is described and an analysis of the potential for perennials to assist in salinity management is presented. The implications of the analysis for farm systems and catchment scale changes in land use are considered. The study highlighted the importance of targeting management decisions to individual sub-catchments and of using relatively detailed farm level models as part of a catchment level study. The potential for perennials to contribute to profitable and robust farm systems and to reduce degradation to land from salt scalds and to streams arising with elevated discharge and wash-off of salt is demonstrated.