Western Australian research has found the use of foliar-applied phosphorus has the potential to improve wheat crop yields in south-western parts of the grain growing region.
Department of Primary Industries and Regional Development (DPIRD) senior research scientist Raj Malik said maintaining an adequate phosphorus supply to crops grown in the high phosphorus buffering index (PBI) soils of south-west WA was challenging.
“Soils with a high PBI lockup phosphorus fertiliser, making it less available to crop plants,” Dr Malik said.
“The most common approach for providing sufficient phosphorus supply to crops on these soils is drilling granular phosphorus fertilisers at sowing.
“This study looked at whether foliar applications could offer a tactical option to ensure an adequate phosphorus supply for crops growing in these soils.”
The research, which has co-investment from the Grains Research and Development Corporation (GRDC), will be presented at the 2025 GRDC Grains Research Update in Perth.
Nine field experiments compared foliar phosphorus applications to wheat across a range of sites near Bannister, Kojonup, Frankland River and Wandering. The experiments were undertaken in farmers’ paddocks where tissue testing showed that wheat was below critical levels for phosphorus.
“Wheat grain yield increased at six out of nine sites due to foliar phosphorus application, with yield increases ranging from 176 kilograms per hectare (4 per cent) to 505 kg/ha (11 per cent) compared to the control where no foliar phosphorus was applied,” Dr Malik said.
“This research has demonstrated that phosphorus deficiency at early growth stages (seedling and tillering) in wheat is occurring in these south-western areas, and that foliar phosphorus has potential to overcome deficiency and increase grain yield.”
Dr Malik said shoot phosphorus concentration at the seedling stage and the soil PBI could be used to guide when foliar phosphorus application is likely to increase grain yield in wheat.
“This study highlights the value of plant tissue testing during early crop growth for detecting phosphorus deficiency in wheat,” he said.
“Our results suggest that a profitable response to foliar phosphorus application in wheat is possible in situations where phosphorus deficiency is occurring at the seedling stage and where PBI (0-10 cm sampling depth) is less than about 180.
“Differing rates of foliar phosphorus application were used in the experiments (2.5 kg P/ha and 5 kg P/ha), with higher agronomic efficiency and economic returns observed at the 2.5 kg rate.”
Further research on use of tactical applications of foliar phosphorus will be continued as part of the GRDC and DPIRD Soil Water and Nutrition (SWAN) strategic soils research collaboration.
The 2025 GRDC Grains Research Update is being held in Perth today (24 February) and tomorrow.
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