Weeds are not yield-reducing on the Jackson’s family farms and that’s how they want to keep it.
Brothers Brad and Phil Jackson farm 2200 ha east of Gurley, in northern NSW with their parents Peter and Janice, and younger brother Matt. The family operation is based on a robust winter cropping program featuring wheat, barley, chickpea, canola and linseed to help keep weed numbers low and manage risk.
Each year there is wheat on about 30–40 per cent of the farmed area and several break crops. If weed numbers start building up in a paddock they use a canola–chickpea double break to help drive down the weed seed bank.
“We see annual ryegrass coming – it’s in the district and on our farm,” says Brad. “We know how bad it can get and how quickly herbicide resistant populations develop. We want to stay on the front foot.”
“The rotation that has worked well here is wheat, followed by canola, then barley, then linseed. Linseed can dry out the profile but is important in the rotation to control root-lesion nematodes,” he says. “We don’t grow any summer crops so we use multiple tactics in our winter crops to keep weed numbers low.”
Having used a conventional tined precision planter for 15–20 years, the Jacksons now use a Boss precision planter with coulters on a parallelogram configuration. They are finding the trash flow is better with the coulter and they have more control over the planting depth. This planter enables them to establish chickpea crops from a planting depth of 20 cm.
Brad and Peter attended the 2017 WeedSmart Week in Wagga Wagga where they were convinced of the need to reintroduce the use of pre-emergent herbicides and take every opportunity to mix and rotate herbicide modes of action.
The Jacksons also use strategic tillage and optical sprayer technology in fallow and desiccation in chickpeas and crop-topping in canola to control late winter grasses and early summer grasses harvest weed seed control.
Re-introducing pre-emergent herbicides
In 2018 the Jacksons applied pre-emergent herbicides across 70 per cent of the farm, for the first time in 20 or 30 years. Their aim was to implement another tactic to control ryegrass, phalaris and black oats using pre-emergent applications of trifluralin (e.g. Treflan, Group 3 [D]) and Tri-allate (e.g. Avadex, Group 15 [J]) in linseed crops and trifluralin and prosulfocarb + s-metolachlor (e.g.Boxer Gold, Group 15 [J]) in wheat and chickpea. In the linseed and chickpeas they apply haloxyfop (e.g. Verdict, Group 1 [A]) and clethodim (e.g. Select, Group 1 [A]) in-crop.
The Jacksons find that they achieve better crop establishment with the coulter than would have been possible with their old planter, providing good support for the applied herbicides, even when seasonal conditions do not favour high efficacy in pre-emergent chemistry.
The re-introduction of pre-emergent herbicides into their program has paid off for the Jacksons and delivered excellent in-crop weed control in conjunction with competitive crops.
Optical sprayer to save glyphosate
The Jackson’s WEED-IT optical sprayer has revolutionised their herbicide program, allowing them to spray low weed density paddocks more frequently and target small, fresh seedlings. They also use it to provide a second knock following a broadacre spray on paddocks with high weed numbers. They are finding this to be a great way to reduce their reliance on glyphosate and ensure this useful chemistry is still effective in the future.
“Optical sprayer units are fairly common in this district,” says Brad. “We purchased ours in 2016 mainly to manage herbicide resistance. We couldn’t really justify the investment based on herbicide savings alone.”
“The desiccation or crop-topping operation is the start of our summer weed control program. After rain we use the broadacre sprayer to apply glyphosate plus a Group 1 [A] fallow pre-emergent and then double knock with paraquat using the WEED-IT,” he says. “It is important to start early to target barnyard grass and we are able to spray more often and target small weeds every 3 to 4 weeks if necessary with the WEED-IT. The main summer weeds here are feathertop Rhodes grass, barnyard grass, and button grass.”
The Jacksons expect to see a reduction in herbicide costs over time through the use of the WEED-IT and are able to justify the use of more expensive herbicides that would be uneconomical to apply with a broadacre sprayer to control barnyard grass.
The Jacksons started no-till in 1990, retaining stubble for improved soil moisture infiltration and retention, and to reduce erosion on their black self-mulching clays.
Although they are committed to no-till farming there is a place for strategic use of shallow cultivation with a Kelly chain. For example, in March 2018 they used a Kelly chain on half the farm area to kill small weeds and close the cracks that were allowing the soil to dry out at depth.
“We used the Kelly chain after harvesting chickpea and then planted imi-tolerant canola 10 cm deep. The canola went on to yield 1.2–2.2 t/ha, which was a great result given the season,” says Brad.
Harvest weed seed control on hold
The Jacksons started harvest weed seed control in response to the unwelcome arrival of annual ryegrass. Initially they would implement narrow windrow burning on about 10 per cent of their farmed area. The ryegrass is now well-controlled with other tactics, including the pre-emergent herbicides, and the Jacksons have not done any harvest weed seed control tactics in recent years.
“We found narrow windrow burning very successful using a 700 mm narrow windrow chute and select paddocks based on weed pressure and crop type,” says Brad. “We would delay harvest until the crop straw is fully dry and plan ahead for an extra header if necessary to cover the area. This allowed for the harvester operator to go slower and cut the crop low to make sure the maximum number of weed seed heads enter the front of the header.”
“If the windrow is too big there is potential for it to be blown over. To avoid that, we would turn the chopper fins backwards on our New Holland harvester to make the windrow with the chopper when necessary,” he says. “This condenses the windrow substantially, keeping it knee high rather than waist high.”
Care is needed when doing this as the header can become blocked up, and air from the fan can blow some weed seed out to the side and away from the windrow.
Brad says the key is to get the weed seeds in the front of the header and then to ensure they are concentrated into a zone where they can be managed strategically.
In terms of crop choice, the Jacksons found narrow windrow burning is a good option for wheat and barley provided the stubble load is not too high. It also works well for chickpea, faba bean and linseed because of the low harvest height and lower stubble loads of these crops, however it can be hard to achieve an even flow of material into the narrow windrow. The Jacksons generally avoided narrow windrow burning in canola crops, opting instead for crop-topping as their main tactic to control weeds present at harvest in canola.
While not currently implementing harvest weed seed control, the Jacksons will reintroduce the tactic any time they feel weed numbers at harvest are increasing.
First published May 2019