Australia
June 26, 2013
Research has shown that applying potassium early in the growing season to barley crops deficient in this nutrient can help reduce the impact of some foliar leaf diseases and boost yields.
Past trials conducted by the Department of Agriculture and Food (DAFWA) and funded by the Grains Research and Development Corporation (GRDC) showed that disease-susceptible barley crops deficient in potassium were more prone to powdery mildew and spot-type net blotch.
Potassium is considered deficient at soil test levels of less than 50 mg/kg (ppm) in the top 10 cm.
DAFWA principal researcher Ross Brennan said plant tissue testing for potassium early in the growing season could help protect cereal crops and optimise fungicide use, especially in regions prone to leaf diseases and where potassium deficiency was known or suspected.
“Trials showed that applying potassium to crops deficient in this nutrient – eight weeks after seeding - could reduce leaf disease incidence of powdery mildew and net blotches and was profitable, provided there was enough nitrogen for plants to respond to the extra potassium,” Dr Brennan said.
“Maximum barley grain yields occurred when potassium was applied at 8 to 22 kilograms per hectare and where fungicides were used to control leaf diseases.
“There were no additional disease control or yield benefits from applying potassium to barley at higher rates of 40 to 120kg/ha.
“Extra potassium fertiliser applications did not reduce the incidence of rust in barley or wheat.”
The trials were conducted on sandy soils in a medium rainfall zone in the South Coast region.
DAFWA plant pathologist Kith Jayasena said an integrated cereal leaf disease management system should include fungicide sprays in conjunction with any extra potassium fertiliser applications.
“Potassium fertiliser should be applied six to eight weeks after barley crop emergence, when roots are developed enough to take up this extra nutrient and potential leaching losses are reduced,” he said.
Dr Jayasena is currently conducting further research into foliar potassium applications and their impact on leaf disease and grain yields.
More information about the past potassium research can be found in the DAFWA Farmnote 216 Potassium deficient barley is more susceptible to powdery mildew disease on the DAFWA website www.agric.wa.gov.au
Information about managing barley powdery mildew is available in the GRDC Barley Powdery Mildew Fact Sheet at www.grdc.com.au/GRDC-FS-BarleyPowderyMildew
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