Matching grazing decision points based on soil water and skill of Seasonal Forecast

Summary

Managing climate variability, particularly variation in rainfall, is an important challenge for livestock producers in southern Australia. In this project the roles of stored soil water and seasonal rainfall forecasts in predicting monthly pasture growth rates were explored. Twelve sites were simulated across southern Australia using the Sustainable Grazing Systems (SGS) Pasture model.

The results indicated that knowledge of soil water content can, at least for some times in the year, give valuable information about future pasture growth. For example in autumn at Hamilton in south-west Victoria, if soil water is moderate or high at the beginning of April this indicates above-median pasture growth rates for the following two months. In spring, low soil water in August, September or October indicates a high probability of low pasture production over the following 3 months. While some general patterns were evident, there are considerable differences between sites and pasture systems in the times of the year when pasture growth projections based on soil water content are useful, and results need to be interpreted on a case-by-case basis.

Producer feedback suggested that seasonal rainfall forecasts are not accurate enough to base farm management decisions on, but that the pasture growth projections based on soil water content showed promise to improve decision making at key times in autumn and spring. Further research is needed to assess its value in farm systems decision-making, and to investigate ways to make this information available to producers.