Michael Dodd, Buntine, happy with results from Overwatch in last year's crop

April 23 2022 - 10:00am
Buntine farmer Michael Dodd likes the idea of attacking ryegrass with two different pre-emergent modes of action. The combination of the new pre-emergent herbicide Overwatch and trifluralin achieved great results in 2021.

FOR Michael Dodd, the benefits of deep ripping on certain soil types have been undeniable.

This soil amelioration technique has removed some of his soil's growth constraints.

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The challenge however has been that not only do his crops grow better after deep ripping, it stimulates weeds like annual ryegrass and without good management they can also thrive in the improved conditions.

The whole deep tillage practice has required a fresh approach with a new weed control plan that matches the yield potential.

Mr Dodd farms with his wife Narelle and son Ryan west of Buntine, and like many WA growers they enjoyed an outstanding 2021 season.

Ex-Tropical Cyclone Seroja went through in April and dropped close to 50 millimetres of rain on their farm and they started seeding canola a few days later.

"It was just the perfect start," Mr Dodd said.

"You still have to get rain during the winter and spring, but all the early signs were good.

"On our farm the two biggest weed challenges have been annual ryegrass and wild radish.

"We tend to have them pretty well under control, but for various reasons like after deep ripping, we still get patches that flare up.

"One of those areas was in the deep ripped paddocks in 2020 where we planted wheat."

Mr Dodd said a lot of ryegrass germinated, which created a problem in the wheat that year.

He said the decision was made to plant Roundup Ready (RR) canola last year as a way of tackling the issue.

"After the 2020 deep ripping we thought those areas were worth spending money on," Mr Dodd said.

"We applied 1.25 litres per hectare of the new pre-emergent herbicide, Overwatch, along with 1.5 L/ha of trifluralin, and an insecticide.

"Then we went on with sowing the rest of the RR canola before moving on to the cereal program.

"We've found in the past that even if you have a best possible result with the trifluralin and just 10 percent of the ryegrass comes through, that still presents a problem."

Mr Dodd said tank mixing with Overwatch herbicide was a good decision.

"I saw first-hand the benefit of having the two different pre-emergent herbicide modes of action working together to control ryegrass and it really took the pressure off the rest of the spray program," he said.

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"A few weeks after sowing we had a look at the paddocks with Geraldton-based spray consultant, Bill Campbell - the result was impressive.

"When we scraped the surface soil away, we could see the trifluralin was having an effect on the germinating weeds and any ryegrass that came through turned a magenta colour and then just died from the Overwatch."

Mr Dodd said the consequence of such good early ryegrass control in the canola was that it took the pressure off the spray program at a very busy time of the year.

He said after just the one follow-up glyphosate spray those crops were really clean.

Mr Dodd said they planted seven varieties of RR canola over 2100 ha in 2021 and had a yield average of 2.4 t/ha.

Commenting on deep ripping and subsequent Overwatch herbicide use, FMC technical extension specialist Stephen Pettenon said the use of the herbicide in the year of soil amelioration needed to be thought through carefully.

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"Crop safety when using IBS (incorporated by sowing) herbicides is highly dependent on moving and keeping treated soil away from the crop seed," Mr Dodd said.

"If ameliorating the soil results in a light fluffy soil profile, seed placement is likely to be very variable due to equipment not travelling true."

"FMC strongly recommend growers wait for the soil profile to compact through rainfall, which may take more than one season, before using Overwatch herbicide."

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