GROWERS and agronomists on the Yorke Peninsula have adopted a vast range of management techniques to improve wild grass and weed control in their crops.
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Kadina agronomist Zack Zweck has been at the forefront, conducting trials, varying crop rotations and employing multiple management tools to prevent herbicide resistance.
Mr Zweck said while wild oats had been problematic at times, wild grasses were the biggest issue for YP croppers in the past five years.
"Number one is probably ryegrass, with brome grass not far behind which is constantly an issue on our lighter soils," he said.
Growers had shifted away from a standard three-year rotation of wheat, barley and lentils, according to Mr Zweck, with an increase of hay and legumes into rotations.
"We've got more legumes in the rotation as a break crop so we can spray grasses out," he said.
"The barley has dropped out a bit in the rotations so wheat-lentil-hay or wheat-hay-lentil can be another option.
"Those rotations are shortening to get more legumes, and more lentils, into the rotation with the recent good money for lentils."
Mr Zweck said while lentils could be "choked out early" by wild grasses, there were more herbicide options capable of protecting legumes than cereals.
"We've still got some good chemical controls which we can spray either pre-emergent or post-emergent to clean them up," he said.
"We're relying on our pre-emergents in our cereal rotation a lot, so we're really trying to clean things up in the cereals because the lentils aren't too far away and then it's back into cereals again quite early.
“We're also relying a lot more on herbicides to control a lot of the grasses."
Mr Zweck said herbicide programs had changed, with more spraying and increased herbicide rotation used to help prevent resistance.
“Traditionally in a legume crop we might have sprayed for grass once and today we're quite often doing two sprays for grass," he said.
Mr Zweck said spray rotation had been used to effectively drive each herbicide’s mode of action, while growers had also adopted windrow burning, chaff carts and other mechanical tools to control grasses.
"Keep trying different things and don't rely solely on chemicals to do the job for you,” he said.
"If you're continually doing the same thing, it's not going to end well.
“It's only going to work well for a certain amount of time."
A long history of trifluralin use on the Yorke Peninsula has led to high resistance in wild grasses, according to Mr Zweck, with other sprays also becoming less effective.
"Pre-emergent wise in the legumes the Treflans really aren't doing anything and we've got more and more of the post-emergent sprays,” he said.
“I wouldn't say the grass is resistant yet but it's more tolerant to higher rates of clethodim and Select.”
AW Vater & Co, Kadina, has coordinated trials of pre-emergent herbicide Sakura in lentils in the past three years, with farmer demonstration trials also occurring during the past two seasons.
Mr Zweck said there had been promising results and said the herbicide, which has been recently registered for lentils, was an excellent pre-emergent option.
"That's taking out the initial flush of ryegrass and allowing the post-emergent sprays to work better because there's less population of grass to kill," he said.
Mr Zweck said post-emergent herbicides were most effective in legumes, while some pre-emergents were more effective than others in cereal rotations.
Trials will continue on the YP this year.
“We're looking forward to some new chemistry in the pipeline, seeing how effective it is, if it's safe, particularly on the lentils, which were a bit softer to some of the chemistry," Mr Zweck said.
