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Bringing the Best of Europe to Australia’s HRZ

25 August 2011

AUSTRALIA - Australian crop researchers are looking over the shoulders of scientists in Britain and New Zealand for effective strategies in dealing with diseases such as cereal rust in our high rainfall cropping zones (HRZ).

The Grains Research and Development Corporation (GRDC) is funding key research into disease management as cropping continues to expand into traditionally wetter regions of southern Australia.

The HRZ is considered the new frontier for the nation’s crop production industry but issues such as yield-damaging cereal rust is hampering potential tonnages.

Former Southern Farming Systems (SFS) researcher Rohan Wardle (now Nufarm regional manager for Victoria and Tasmania) says GRDC-funded research allowed the HRZ grower group to explore the principles of disease and canopy management from New Zealand and Europe to increase productivity.

“The GRDC funding has enabled SFS to run a series of about 20 trials per cropping year with data generated on both canopy manipulation and the latest fungicide technology,” Mr Wardle said.

“The findings were extremely topical in light of recent stripe and stem rust outbreaks which left many growers and advisers ill equipped with the knowledge to manage disease with fungicides, as a consequence the technology transfer element of this project was critically important.”

Freyr Colvin, Southern Farming Systems monitors trials at Inverleigh, Victoria.

Mr Wardle said the research showed foliar fungicide strategies and timing needed to be related to the emergence of key leaves as well as the onset of infection, in order to secure benefits from these inputs.

“In wheat flag leaf emergence or growth stage GS39 was pivotal to any fungicide strategy,” he said.

“If onset of stripe rust occurred before flag leaf emergence, foliar fungicides were unable to protect the flag leaf.

“Assuming disease was present, commencement of spraying at GS32 (second node - emergence of flag -2) resulted in the need to spray again at flag leaf emergence GS39, while spraying at GS33 (third node - targeting the emergence of flag -1) gave greater flexibility to use a second spray to combine a flag and early ear emergence spray at GS55 (50pc ear emergence on main stem).”

“Where economic advantages were secured was in situations where crops had higher yield potential (about 5t/ha) and were under severe early infection or where leaf rust was the principal disease,” Mr Wardle said.

“Results illustrated that unpredictable conditions during grain fill will dictate that fungicide cost needed to be kept at a minimum in order to secure a return.

“In stripe rust infected wheat disease control could be achieved for about $10/ha, giving a cost benefit of at least 2:1 as long as infection occurred during stem elongation (GS30-39).

“In barley, disease was less easily controlled by $10/ha expenditure and the key fungicide timing was earlier than wheat, first node to third node (GS31-33) depending on onset of infection.”

Mr Wardle said trials where water supply was regulated found that water availability during grain fill increased the difference in green leaf retention between treated and untreated crops and increased disease pressure due to canopy density.

The level of fungicide expenditure needed to be related to rainfall probability post application.

A canopy management husbandry approach resulting in thinner, less vegetative crops produced similar yields to thicker crop canopies fertilised with seedbed nitrogen, although other benefits did become apparent during the project, Mr Wardle said.

“It was illustrated that thinner crop canopies resulting from later applied nitrogen GS30-31 were more likely to produce higher protein content (up to 1pc), indicating greater nitrogen efficiency.

“In barley in particular it was noted that less vegetative crops produced larger grains and as a consequence lower screenings and higher test weights.”

Mr Wardle said in low rainfall areas the delayed nitrogen approach had the benefit of allowing better decision making on whether to apply nitrogen to the crop, since the seasonal outlook is more accurate in late August (early stem elongation) than it is at sowing.

“In addition it allows better use of predictive crop models such as APSIM and spring rainfall predictions based on the southern oscillation index.

“The GRDC-funded research showed individual site yields were not linked to tiller population and that similar yields could be generated off of crop canopies with fewer ears per square metre and better crop canopy duration.”

TheCropSite News Desk

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