Defining risk of P in runoff
From the December 2008 edition of Agriculture Today.
A recently developed rainfall simulator will assist researchers improve the reliability of risk management of phosphorus (P) in grazing systems.
A new project using the simulator will improve the ability to predict runoff P losses on a wide range of soils, according to research scientist, Dr Warwick Dougherty.
"The research will be highly practical and likely to be readily adopted by industry," Dr Dougherty, based at Richmond with the NSW Department of Primary Industries (DPI), said.
It was well established P contained in runoff from pastures could contribute to eutrophication of waterways but the current ability to accurately predict runoff P concentrations was poor and was based on a small number of trials.
"We know relationships between soil P and the amount of P in runoff vary greatly between soils, greatly limiting our capacity to accurately prioritise soils for remedial actions," Dr Dougherty said.
"This is a problem for farmers and catchment managers seeking to invest in remedial works.
"Combining new techniques with existing routine soil test information and knowledge of fundamental soil chemistry, we propose that we can greatly improve our risk assessments."
The key tool grazing industries used to assess nutrient loss risk was the recently developed Farm Nutrient Loss Index (FNLI).
Dr Dougherty said the new research would make a major contribution to improving the accuracy of risk assessments provided by the FNLI.
The collaborative research with Dr Lucy Burkitt of the Tasmanian Institute of Agricultural Research’s Dairy Centre, and Paul Milham of NSW DPI would use the recently developed rainfall simulation techniques.
Dr Dougherty and Dr Burkitt developed the new technique over the past five years, building on US research.
"From our development research, we know how the data generated relates to real situations, giving us great confidence in applying it," he said.
"The technique will allow us for the first time to carry out research on a wide range of soils under controlled conditions.
"Normally we would need multiple field sites which are costly to run.
"Furthermore, climatic and site variability normally makes the research difficult to undertake."
Dairy Australia, will fund the research over the next 12 months, as a precursor to a broader ranging study it is considering.
Contact Warwick Dougherty, (02) 4588 2112, warwick.dougherty@dpi.nsw.gov.au
