McFadyen family, Lake Cargelligo NSW

Andrew accumulated extensive experience working as a commercial agronomist and then cropping and senior manager with Paspaley Pearls Properties based at Kurrajong Park, Coolah in NSW, before returning to the northern Riverina low rainfall zone. As chairman of Grains Orana Alliance (GOA), he is keenly interested in conducting and evaluating field research that addresses information gaps as they emerge at the local level.

“At Wilga Park, we have a mixed farming system that suits the two generations involved and provides good weed control options,” says Andrew. “Ryegrass and black oats are the most challenging weeds in our cropping system, with resistance, mainly to glyphosate, being very common across the region.”

While working at Coolah and on the Liverpool Plains, Andrew had seen patches of grass weeds surviving glyphosate applications, and started sending samples for herbicide resistance testing, then discussing management tactics to manage this emerging problem.

“Within my client group we are now doing the same – testing suspect plants and sharing experiences and management results within the group to raise awareness and keep one step ahead,” he says.

Lake Cargelligo is in the northern Riverina low rainfall zone, which has an annual average rainfall of 425 mm distributed evenly throughout the year. The region has experienced a string of unusually wet years from 2023, including significant flood events.

There is a farming system and soil type effect from north to south in the region. To the north, the soils are heavier, and annual ryegrass is becoming increasingly difficult to manage in the mostly continuous cropping systems. To the south, the soils are lighter textured and feathertop Rhodes grass is the most challenging weed in cropping paddocks.

The Mallee sands with red clay (sometimes sodic) subsoils typical of the Lake Cargelligo area present some management challenges for weed management, pre-emergent herbicides, and crop germination. Andrew uses the WeedSmart Big 6 framework to build a program to suit the grower, selecting a suite of tactics that the grower can implement within their farming system.

At Wilga Park, the McFadyens crop 30 to 40 per cent of the aggregation and run trade lambs on the remaining area. Their cereal-dominant rotation is in place for three to four years with the final crop undersown with lucerne and the sheep returning to the paddock after harvest.

Within Andrew’s client group, there is a broad mix of cropping systems, including irrigated cotton and some forage sorghum in summer, and wheat, barley, canola, lupin, chickpea and vetch (brown manure and hay) in winter.

“On mixed farms like ours, a lucerne and pasture phase has similar outcomes to growing vetch in continuous cropping systems,” he says. “Both build soil nitrogen, and combat problem weeds, either with grazing and alternative herbicide modes of action, or through brown manuring or making hay to eliminate weed seed set.”

Within his client group, the average scale of operation for cropping is 3000 ha total area (2000 ha crop, 1000 ha sown chicory, fescue, lucerne pasture), along with larger mixed farms of 5000 to 30,000 ha that include large sections for extensive grazing that are not cropped.

Many farms in the Lake Cargelligo area are intergenerational businesses where profitability is the key driver for decision-making. Andrew encourages growers to look outside their district for challenges and to see what’s coming, while cultivating a community culture of social mingling and peer-to-peer learning at the local level.

“When working with clients and within our own operation, we try to ‘control the controllables’,” says Andrew. “By keeping focus on the things we can control, like crop rotation, product choices and spray application logistics, the uncontrollables, like seasonal conditions and existing herbicide-resistant weeds, tend to have less impact. Every decision has trade-offs, so the best you can do is work towards the goals for the business.”

Andrew used the WeedSmart Big 6 framework to ensure each integrated weed management strategy includes as much diversity as possible to keep weed numbers low.

#1 Crop and pasture rotation

A typical mixed farming rotation includes a 3 to 5-year cropping phase (growing wheat, barley, and canola), with the final year commonly oats, under sown with lucerne, to begin a 3 to 5-year pasture phase. Lucerne or lucerne plus oats provides additional protein for lamb growth, along with opportunities for alternative weed management tactics, including strategic cultivation.

“The lucerne phase needs to be at least two years long to provide effective weed control,” says Andrew. “We can implement a range of tactics in this phase, including pasture topping with paraquat, hay making, grazing, grass-selective herbicides, such as clethodim targetting ryegrass and barley grass mainly, and strategic cultivation.”

Andrew says the double-knock effect of pasture topping followed by heavy grazing pressure using large flocks of sheep is an excellent way to stop weed seed set.

In a minimum-till, continuous cropping system, the most common rotation is wheat, canola, wheat, but growers also need another option if there’s insufficient soil moisture at planting for canola. Vetch has proven to be a good break crop that growers are willing to plant. Growing vetch enables weed control options similar to those used in a pasture phase. Andrew says controlling grass weeds is particularly important to conserve the nitrogen fixed in the soil during the legume phase.

Adding herbicide-tolerant crops to the rotation has many benefits, provided that they are part of a well-planned rotation. Andrew says he is always discussing scenarios within his grower group, to avoid panic decisions when things don’t go to plan.

“In this area, we can use several imi-tolerant Clearfield crops to manage grass weeds, provided we are intentional about avoiding being caught in an imi-spiral,” says Andrew. “We plan as far ahead as possible to ensure effective weed control, minimise resistance risk and protect crop safety. For example, an imi might be applied in Clearfield canola, then no imi herbicide applied in the following Clearfield wheat crop, and an imi applied in the following Clearfield barley.”

Each of these crops also offers other weed control options to suppress germination and stop weed seed set.

In continuous cropping systems, wheat is the pillar crop with barley providing a good alternative in drier years. Andrew says grower interest and confidence in canola has grown in the last five or six years, since the establishment of National Variety Trials (NVT) for canola in the local area. These trials have demonstrated canola’s ‘fit’ for weed and disease management, and profitability in different seasons. Growers are also gaining experience and confidence using pre-emergent herbicides with canola, which is expanding the weed control value of this crop in the rotation.

“Canola is a great option in the Lake Cargelligo area when there is good soil moisture at planting, and a favourable forecast,” says Andrew. “Heat and low humidity in spring can impact canola crops here. Our spring is generally very short, ahead of a prolonged summer. Sowing early is critical to achieve rapid growth in winter and early spring. For us, hot days during flowering is of more concern than frost.”

Andrew says that having an overall rotation with built-in flexibility is beneficial. For example, being aware of the possible implications of using particular residual products, such as Lontrel, that have long residual effects under some conditions.

“In the fallow, maintaining stubble cover and eliminating weeds are very important, particularly on our lighter soils, to conserve soil moisture,” he says. “Every 1 mm of water conserved equals 15 to 20 kg of grain per ha in this region.”

In mixed farming systems, sheep need to follow the spray rig after harvest. Andrew says more growers are retaining stubble to conserve soil moisture and only burning when the stubble load is likely to interfere with planting equipment. Growers are also harvesting at increasingly lower heights. There is also slow adoption of stripper fronts that leave tall standing stubble to provide maximum shade of the soil surface, which conserves moisture and suppresses weed germination.

“The stripper fronts work very well in cereals, but some growers are concerned about canola stubble not providing enough protection of the soil,” says Andrew. “Some cut canola crops short, while others slash, graze, or leave the stubble standing.”

#2 Crop competition

Local trials conducted by Maurie Street and the GOA team demonstrated the value of increasing crop competition through higher seeding rates, especially in drier years.

“This research upended some local rules of thumb and gave growers and agronomists very valuable information for this region,” says Andrew. “Previously, wheat was commonly sown at a rate of 30 kg seed per ha, but these trials showed that increasing the sowing rate to 40–50 kg/ha produced healthy, competitive crops without a yield penalty.”

Most growers in the region prefer slightly wider rows (mostly 22.5 to 30 cm, some at 37.5 cm) for easier stubble management at planting and better efficacy of pre-emergent herbicides. About 90 per cent of the cropped area in the region is sown using tyne seeders.

Andrew says the focus on fallow efficiency in the LRZ tends to override a move to narrower crop rows. He encourages growers to adopt other competitive cropping tactics, such as higher seeding rates and competitive varieties, particularly in weedy paddocks.

“In paddocks where weed numbers are increasing, choosing a competitive barley variety plus a robust herbicide package is an excellent strategy to drive down the weed seed bank,” he says. “Yield is always the first consideration when choosing crop type and variety, and there is often only one planting opportunity in low rainfall zones like ours. We choose the most suitable and competitive variety based on the planting window and sow as early in the window as possible without compromising the frost risk.”

#3 Spray efficacy

Andrew works actively with his grower group to focus on spray efficacy and application efficiency. The spray windows are often very short, so growers need to have sufficient spray capacity to cover their cropped area in 7 to 10 days. There is increasing use of contractors in the region to ensure timely applications – targeting small weeds while they are actively growing and applying the second knockdown herbicide within the optimal timeframe.

“Storing soil moisture and nitrogen over summer is critical for successful winter cropping,” says Andrew. “For double-knocks, some growers spray first, then graze, and others use combinations such as glyphosate + Group 14 spike followed by paraquat or glyphosate followed by paraquat + Group 14 spike.”

He says flaxleaf fleabane is the main target for the double-knock tactic in fallow, depending mostly on when the summer rain falls.

The WAND (Weather and Networked Data) towers in the Lake Cargelligo area have generated good discussion amongst growers and provide useful information when growers are planning spray operations.

“In summer, there are sensitive crops such as cotton growing in this area, and the WAND towers have helped minimise spray drift, resulting in less crop damage,” he says. “The 2023-24 summer was a big spray volume season, and minimal drift issues were identified in this area.”

“Low spray drift also means that more product is hitting the intended target, which is the best outcome for weed control.”

He says growers are conscious of the need for herbicide stewardship to slow the path to resistance and to protect sensitive crops and environments. This involves minimising drift, upskilling operators and ensuring herbicides are applied when conditions support maximum impact on the target weeds.

The adoption of optical spot spraying technology and automation was low in the Lake Cargelligo area, but Andrew says that the spread of feathertop Rhodes grass has driven increased uptake in the region in recent years.

#4 Mix and Rotate modes of action

Growers in the region understand the ‘mix and rotate’ modes of action concept well. Andrew says there has been a good transfer of knowledge, and growers are asking their agronomists important questions when planning their crop rotation and herbicide program.

“They want to access the best available knowledge and to know how to do things better next year,” he says. “As a result, there is rapid adoption of practices and products that work. The ‘don’t stick to a good thing’ message has hit home, and growers are mixing modes of action as much as possible and rotating away from products that are doing a good job, to keep them effective.”

Crop choice essentially drives herbicide rotation and options. Andrew says the Predicta B test for disease also influences crop choices, given that the risk of yield loss is associated with the level of pathogen DNA detected in the soil. Poor soil health is also associated with increased weed pressure due to reduced crop competition in patches or across the whole paddock.

Residual herbicides are commonly used in fallow in wet years, usually as a post-harvest control tactic against sowthistle and feathertop Rhodes grass, and growers plan their chemical use to avoid plant-back issues in the planned following crop.

Pre-emergence herbicides have a shorter history in the Lake Cargelligo cropping systems compared to many other regions. Andrew says growers are gaining a better understanding of how to use these chemistries effectively, and so confidence is also building.

A string of uncommonly wet winters in the Lake Cargelligo region led to a buildup of annual ryegrass in crops, and in 2024, Andrew implemented a planned pre-emergent herbicide strategy using Overwatch on his own farm and within his client group.

“Ahead of the 2024 season, we ran an education program and discussed realistic expectations around pre-emergent herbicides within our client group,” he says. “A key component was understanding the importance of timeliness and planter speed. It can be hard to get people to slow down at planting until they see that the trifluralin didn’t kill the crops; sowing speed did.”

When growers reduce the planter speed by 0.5 to 2 km/hr, they see the benefit in less crop damage and better weed control, says Andrew. They are now asking their agronomists more questions about what they can do to make the products work well. It’s the consultant’s role to recommend different tactics to suit the paddock history, weed spectrum and resistance status, keeping older and cheaper chemistries in the program for as long as possible, and introducing cost-effective new technologies.

#5 Stop weed seed set

Windrowing and pre-harvest crop topping in canola are effective tactics used in the area to stop weed escapes, particularly annual ryegrass, from setting seed late in the season.

Spraying out vetch and lucerne or spraying under the cutter bar when windrowing canola is another very effective tactic for stopping weed seed set. For new incursions, Andrew says patch management with cultivation is often a good immediate solution.

In cotton, there is a heavy reliance on glyphosate, but the industry is complying with the stewardship requirements for the herbicide-tolerance traits available to them. Cotton is commonly grown in rotation with durum wheat, with a long fallow between crops to control weeds and store soil moisture.

Weed management in non-cropped areas is a weakness on most farms. Glyphosate resistance, particularly in annual ryegrass, develops in irrigation channels and drains, and along fencelines, then the seed blows into the fields.

#6 Harvest weed seed control

To date, the adoption of harvest weed seed control tactics in the Lake Cargelligo area has been low. This is mainly due to the region’s low incidence of herbicide resistance, resulting from a shorter history of minimum tillage farming systems. A few growers use narrow windrow burning strategically, and more growers are beginning to discuss other harvest weed seed control options.