Hot narrow burn keeps weed seeds down
GroundCover™ Issue: 124 | Author: Alistair Lawson
Narrow windrow burning canola as part of a broader integrated weed management strategy has played a vital role in driving down weed seed numbers for the Jaeschke family at Hill River.
Farming in a high-rainfall area just south-east of Clare in South Australia’s Mid North, the Jaeschkes have been narrow windrow burning for five years.
It is a low-cost practice that involves a chute being set up on the back of a harvester to drop chaff into a narrow row during harvest for burning in autumn.
The Jaesckhes – Grant and his wife Megan, Craig and his wife Nicole, and parents Rob and Lyn – crop cereals, pulses and oilseeds across 3000 hectares with a typical rotation comprising faba beans or canola/wheat/oaten hay or, with a heavy weed burden, beans/canola/wheat/hay/hay.
Problem weeds on the Jaeschkes’ property include annual ryegrass, wild radish and wild oats. As no-till croppers for 20 years, Grant says the family has worked on rotations and integrated weed management to help reduce reliance on chemicals. However, they still use chemical control strategically in the lead-up to harvest.
Canola is crop-topped or sprayed under the windrow with Weedmaster DST®. Faba beans are crop-topped with paraquat.
Hay crops are sprayed out with glyphosate and once it is cut, baled and carted, the paddock receives a blanket spray of paraquat to kill any surviving weeds. But it is the narrow windrow burning in canola crops that brings the most pleasing results for the Jaeschkes.
“Narrow windrow burning was a big decision for us,” Grant says. “We are very anti-burning and it was a big step for us to burn any part of a paddock.”
Initially the Jaeschkes worked with the Hart Field Site Group (HFSG) to quantify the results of narrow windrow burning. That turned out be a great experience with results coming back indicating 95 per cent destruction of annual ryegrass seeds.
Since then, the Jaeschkes have continued to monitor ryegrass numbers following a narrow windrow burn and continue to record weed kill percentages in the high nineties.
“We had excellent results straight off the bat,” Grant says. “We couldn’t fault it when we did the initial trial and the data generated by Hart was invaluable.”
Canola crops are cut at about 30 centimetres high at windrowing, which Grant says captures the majority of ryegrass seed heads without compromising the canola windrow. The Jaeschkes set up their narrow windrow burning chute aiming for a row between 30 and 40 centimetres wide.
“We try to make the row as narrow as possible without plugging up the header,” Grant says.
“However, we normally put sheep on canola stubbles straight after harvest and they burrow into the row to find seeds so the row might get spread out to 50cm.”
Windrows are left over summer before being burnt in autumn. Grant says the key to getting a good burn is “a bit of luck” as conditions have to be right.
“The rule of thumb is to have a 10 kilometre per hour wind blowing at a slight angle to the row,” Grant says. “We want the burn to last for about a minute or so at a minimum of 400ºC in the same spot.
“It can be a bit of a process to get it right but we have learned there is no area we can really neglect. It’s very obvious if we haven’t got the burn right in a cereal following canola because there are ‘tiger stripes’ of ryegrass through the wheat crop.
“In high-rainfall zones, if you get a wet year and miss the ryegrass there are going to be five years of pain after that so it’s critical to get it when you can. We have missed it before, harvesting a wheat crop that yielded one tonne per hectare purely because of weed burden when we’d like to average 4.5t/ha to 5t/ha.”
The Jaeschkes obtain permits from their local council to undertake burns during the fire ban season, otherwise rain that falls by the end of the fire ban season makes it difficult to burn.
“We did have one year where we had some really heavy summer rain, which is something you can’t really manage,” Grant says. “It is normally a case of waiting for a bit more wind so we can get more heat in the windrow and get a good burn, but with a wet windrow we normally drop below 50 per cent weed kill.”
Pest kill bonus
An added benefit to narrow windrow burning for the Jaeschkes has been pest management.
“We were getting wiped out with millipedes, slugs and snails, but since we’ve been narrow windrow burning we’ve been able to halve our baiting,” Grant says. “For us, that’s a huge benefit.”
Despite some of the challenges, Grant says having an integrated weed management strategy incorporating crop rotations, spray topping, hay, livestock and narrow windrow burning significantly reduces the weed burden across their farm.
“There are plenty of tools in the toolbox and, as a result, the weed burden is quite low,” he says.
“We took on some lease country about five years ago with a heavy ryegrass burden and now we’re battling to find a ryegrass plant out there.
“Our weed management strategy might seem over the top but with dry springs becoming more prevalent, every weed is another competitor for moisture.”
More information:Grant Jaeschke,
0413 690 450,