Western Australian grain growers can make significant cost savings by reducing phosphorus application to ‘maintenance rates’, and using soil test results to fine-tune them.
CSIRO principal research scientist Mike Wong told recent Regional Crop Update events that 87 per cent of WA wheat paddocks had reached and exceeded ‘critical values’ where there were negligible yield gains from phosphorus build-up beyond these values.
He said WA grain growers were, on average, applying almost twice the amount of phosphorus required and could save $9.60 to $14.20 per hectare without losing productivity or reducing soil phosphorus levels.
“Researchers need to determine the ‘maintenance rates’ required for different soils and regions of WA so reliable maintenance recommendations can be made for growers,” Dr Wong said.
“In the meantime, I encourage growers to soil test and if phosphorus levels are above critical values, they should reduce application rates.
“They should then monitor soil and plant phosphorus concentration levels to fine-tune those application rates.
“Growers who are apprehensive about reducing application rates can use strip trials before applying them to whole paddocks.
“Areas deficient in phosphorus are likely to be small and can be mapped.”
Dr Wong said growers had successfully built up phosphorus levels over the decades, and now should focus on maintenance to ensure that status was not lost.
Mike Wong of CSIRO.
“Maintenance aims to sustain the soil phosphorus status at adequate levels by replacing amounts removed in harvested products, fertiliser phosphorus tied-up in the soil and unavoidable losses.”
Dr Wong said sandy soils tended to lose more phosphorus to leaching than loams, while early-cleared land tended to contain higher levels of the nutrient.
He said money saved from reducing phosphorus applied should be reinvested to treat commonly occurring soil constraints such as acidity and potash deficiency.
“Growers should also be aware that in some soils, severe water repellence, severe acidity and the presence of root diseases may increase the apparent critical soil phosphorus level required by crops,” Dr Wong said.
The phosphorus research was conducted as part of a $1.2 million GRDC funded project investigating the variation in nutrient supply and demand in crops.
It was complemented by research into dairy, meat and sheep pastures funded by Meat & Livestock Australia and CSIRO Sustainable Agriculture Flagship.
CSBP provided WA soil test data underpinning the work.
The Regional Crop Updates provide WA growers with practical new, locally relevant information on crop disease management, nutrition and agronomy.
Supported by the GRDC and the Department of Agriculture and Food (DAFWA), 14 updates were held throughout the grainbelt in March.
More information to help growers make informed decisions about phosphorus fertiliser application rates can be found in the GRDC western region Crop Nutrition Phosphorus Management Fact Sheet, available at www.grdc.com.au/GRDC-FS-PhosphorusManagement
Video Caption: Mike Wong of CSIRO and Kit Leake GRDC Western Regional Panellist.
PHOTO CAPTION: CSIRO principal research scientist Mike Wong addresses growers at the Regional Crop Update at Broomehill, hosted by Southern DIRT.
PHOTO CAPTION: CSIRO principal research scientist Mike Wong
AUDIO DOWNLOAD: Click here to download and audio grab for this release. Audio is of Mike Wong.
Mike Wong, CSIRO
(08) 9333 6299
Natalie Lee, Cox Inall Communications
(08) 9864 2034, 0427 189 827
GRDC Project Code
West, National, North, South