Assessing field sediment exports of northern Victoria farming systems using HowLeaky2008 model

Australian agriculture is under pressure to reduce sediment exports and improve stream water quality. However data on soil losses of different land management is lacking, thus potential benefits of adopting Best Management Practices cannot be quantified. In this study we assessed field soil losses of farming systems of North Central Victoria by using the HowLeaky2008 model. HowLeaky2008 is a one-dimensional farm system model that simulates the effect of soil and land management on daily water, sediment and nutrient exports. HowLeaky2008 was applied to current and alternative land management options in the Avon Richardson catchment, which is typical of the Wimmera-Mallee region of Victoria. Simulated long term average soil losses were similar to erosion rates previously assessed with 137 Cs techniques. Modelling suggests that changing from minimum to zero tillage can reduce sediment exports by 40-75% in cropping land; and switching from annual to perennial pastures or lucerne can reduce sediment exports by over 80%. Highest erosion rates and potential for reducing sediment exports were on duplex soils followed by Kandosols and Red or Grey Vertosols. The HowLeaky2008 model proved useful to quantify the relative efficacy of farming practices that improve the environmental sustainability of agricultural enterprises.