Op­por­tu­ni­ties to re­duce weed man­age­ment costs

Australian Farmers & Dealers Journal - - NEWS -

OP­POR­TU­NI­TIES ex­ist for grain grow­ers in Aus­tralia's south­ern crop­ping re­gion to more ef­fec­tively man­age weeds in re­tained stub­ble sys­tems, ac­cord­ing to new re­search con­ducted by the CSIRO and funded by the Grains Re­search and De­vel­op­ment Cor­po­ra­tion (GRDC). CSIRO Senior Re­search Sci­en­tist (Farm­ing Sys­tems) Dr Rick Llewellyn says the new study has high­lighted just how costly weed man­age­ment has be­come and where there are op­por­tu­ni­ties to re­duce fur­ther cost in­creases. Pre­sent­ing at a meet­ing of farm­ing sys­tems groups in­volved in the GRDC's south­ern “stub­ble ini­tia­tive”, Dr Llewellyn said data col­lected through a study of 600 grain grow­ers' weed man­age­ment prac­tices showed that while there has been re­cent rapid up­take of some key IWM prac­tices across the south­ern crop­ping re­gion (South Aus­tralia, Vic­to­ria, Tas­ma­nia and south­ern and cen­tral New South Wales) there were still many ar­eas where adop­tion re­mains low de­spite the her­bi­cide resistance threat. “The data shows very large dif­fer­ences be­tween re­gions for prac­tices like har­vest weed seed con­trol, crop top­ping and dou­ble knock­down which re­flects past dif­fer­ences in the lev­els of her­bi­cide resistance, but we're now see­ing resistance is­sues be­com­ing much more im­por­tant in all crop­ping re­gions,” Dr Llewellyn said. “Many south­ern farm­ers have not yet faced the same her­bi­cide resistance cri­sis that has come about in Western Aus­tralia or crop­ping-in­ten­sive parts of the medium rain­fall zone, such as the Mid North of SA, but now there's the chance to make ear­lier use of some of the prac­tices that have been re­fined through farmer ex­pe­ri­ence to ex­tend the life of im­por­tant her­bi­cides, not just con­trol re­sis­tant weeds once her­bi­cides are lost. “Where an in­te­grated weed man­age­ment prac­tice can be in­tro­duced rel­a­tively cheaply we're see­ing that grow­ers are very will­ing to take up the prac­tice and nar­row windrow burn­ing is an ex­am­ple of that.” While rye­grass re­mains the most com­monly re­sis­tant weed, changing weed dy­nam­ics in the south­ern crop­ping re­gion mean that long-term strate­gies are in­creas­ingly needed for con­trol of other grass weeds as well, ac­cord­ing to Dr Llewellyn. “Brome grass in par­tic­u­lar is re­ally in­creas­ing in its spread and im­por­tance in much of the re­gion. Re­cent stud­ies have shown how brome has risen up the charts in terms of costs to grow­ers and im­pli­ca­tions com­pared to a decade or two ago. “Rye­grass has re­ceived a lot of the at­ten­tion in Aus­tralia in the past but we're now work­ing with the Univer­sity of Ade­laide weeds team to look at the most eco­nomic long-term strate­gies of man­ag­ing brome which has be­come the driver grass weed for a lot of our crop­ping land – it's a weed for which there aren't a lot of her­bi­cide op­tions and har­vest weed seed con­trol meth­ods aren't al­ways highly ef­fec­tive. And what her­bi­cides op­tions there are, are be­ing placed un­der a lot of pres­sure. “There is a re­quire­ment of farm­ers to care­fully man­age the her­bi­cide op­tions they have over time. We're aim­ing to help farm­ers and ad­vis­ers take a longer-term seed­bank and resistance risk view, by con­sid­er­ing when they should use these her­bi­cides to get the big­gest bang for their buck and not use them up too quickly, as well as look­ing at the longer-term value of in­tro­duc­ing new weed man­age­ment prac­tices.” Dr Llewellyn said the lat­est study had also shown that sum­mer weeds were likely to be now caus­ing more crop yield loss than winter weeds. “This is partly be­cause, de­spite the chal­lenges, grow­ers are con­tin­u­ing to keep winter weed den­si­ties in crop quite low, partly be­cause sum­mer weeds are be­com­ing in­creas­ingly dif­fi­cult and costly to con­trol and partly be­cause stored mois­ture is so of­ten of very high value to crop pro­duc­tion. “Even though about two thirds of land for crop­ping in the south­ern re­gion may re­ceive a her­bi­cide treat­ment for sum­mer weeds and about a third of grow­ers use at least some cul­ti­va­tion for sum­mer weed con­trol, we are still see­ing high to­tal costs to yields from sum­mer weeds. “It's a part of the farm­ing sys­tem that is in­creas­ingly costly and is in need of more man­age­ment op­tions, par­tic­u­larly as new her­bi­cide re­sis­tant or her­bi­cide tol­er­ant sum­mer weeds be­come more im­por­tant,” Dr Llewellyn said. • De­tails: www.grdc.com.au/re­sources/IWMhub.

CSIRO Senior Re­search Sci­en­tist (Farm­ing Sys­tems) Dr Rick Llewellyn says a new study has high­lighted just how costly weed man­age­ment has be­come and where there are op­por­tu­ni­ties to re­duce fur­ther cost in­creases. Photo: C. Sul­li­van.

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