Read time: 4 minutes

Krui Pastoral Co, Condamine, Qld

East-west sowing between shade lines

Half an hour west of Condamine on the western Darling Downs, Jake and Felicity Hamilton work with Jake’s father to farm 4500 ha of brigalow scrub, which was originally cleared for cattle grazing in the decades since 1975. Although the cattle are all gone now, the Hamiltons have maintained the shade lines of native vegetation left when the property was cleared and which occupy about 10 per cent of the farm’s area.

Jake says the thick stand of buffel grass in the shade lines prevents other weeds from establishing and the buffel doesn’t move into crop areas. Most of the fencelines are also timbered, with the low soil moisture keeping a lid on weeds.

Jake and Scott Hamilton, are well aware of the impact of herbicide resistance on their farm near Condamine, Qld.

“When the farm was cleared, the shadelines were left running east west to maximise the shading effect for the livestock and now we are cropping east west in fairly large, square paddocks,”says Jake. “We are now taking advantage of the shading effect on the inter-row to suppress weed germination and growth.”

Crop rows run east-west, parallel with tree lines left when the property was cleared, to provide shade for stock.

Growing wheat / chickpea / wheat, with few opportunities for summer cropping in recent years, Jake has been working hard to keep on top of herbicide resistance in summer growing species including barnyard grass, liverseed grass, button grass and feathertop Rhodes grass.

Not being able to grow summer crops on a regular basis, Jake has implemented a robust fallow management program to keep these weeds under control.

“We try to double knock the glyphosate applications with paraquat, especially if the weed burden is high, there are large weeds present or weeds are not dying like they should,” he says. “And we always use full label rates to avoid herbicide resistance.”

Jake regularly employs casual labourers to go around the farm on the ‘Gator with the spot spray rig to deal with any individual weed survivors, or if there are weedy patches they use the 6 m boom on the ‘gator’.

Spot and patch spraying is time-consuming but very worthwhile.

“Spot spraying summer grasses is quite time consuming but incredibly effective and cost efficient,”he says. “We also employ an agronomist to visit the farm once a fortnight to assist with monitoring and planning the weed control program.”

“We know we are losing Group M [glyphosate] and can see resistance to Group A [grass selective] chemistry on button grass, which will leave us with very few herbicide options. We rotate crops as best we can so we can use different methods of weed control to try and break the resistance.”

Button grass is proving to be quite a challenge to control with herbicide.

Following two reasonable winter seasons, the 2016–17 summer was too hot for summer cropping, with no rain falling between September and February. Jake took this opportunity to do more laser levelling to remove the melon holes that are characteristic of brigalow scrub soils. Levelling brings about an immediate increase in yield and more even crops.

“We purchased a second hand Caterpillar D11R and fitted it with TopCon GPS,”says Jake. “With the dozer we are able to cut 10 cm below grade on our first pass, which creates a good blend of topsoil with any exposed subsoil to avoid ‘scalping’the paddock.”

Every four years the Hamiltons also incorporate 10 t/ha of manure to a depth of 15 cm and plan to utilise variable rate technology to apply manure to ameliorate some areas of soil fertility decline.

“After using a chisel plough for several years to incorporate the manure, we are moving toward a program of deep ripping and deep application of phosphorus fertiliser to a depth of 40 to 50 cm, on 50 cm spacings,”says Jake.

Since 2001 the farming system has been controlled traffic with 12 m bays, to suit 36 m sprayer, 24 m planter and 12 m header. Their new planter is configured for 375 mm (15″) spacings for wheat and barley, 750 mm (30″) for chickpeas, faba beans and mungbeans and 1500 mm (60″) sorghum and cotton. Jake also uses high seeding rates to maximise crop competition, along with their efforts to improve overall soil fertility and boost crop competitiveness.

Although there are some risks associated with the short crop rotation Jake says residuals are doing a good job controlling weeds in-crop, with no late germinations evident. “We use residuals plus picloram and aminopyralid for fleabane control in wheat,” he says. “In chickpea we apply simazine and Balance and follow with an in-crop application of a Group A herbicide.”

“If there are weeds present in-crop they usually don’t seed before harvest,” he says. “Black oats is a potential problem though if there is a spray miss.”

They also apply pre-emergence herbicides Balance + Flame + diuron in some paddocks to keep them clean over summer while leaving their summer cropping options open in other paddocks.”

The Hamiltons store planting seed on farm and grade all their seed through a mobile grader on the Easter long weekend, aiming to achieve a good clean sample –99 per cent purity.

Jake spreads their frost risk by planting 50 per cent of the wheat area to Gregory in early May then sowing the chickpea area the following week. The remaining wheat area is sown later to Suntop or Crusader.

After suffering severe frost damage in late August 2017 the Hamiltons changed their planting schedule to reduce their frost risk. Jake says late frosts can be a problem in the Condamine area and can badly affect chickpea crops if the temperature drops to zero or below during flowering or podding.

“We aim to have all our wheat planted between 7 and 21 May and then plant chickpeas after that,”he says. “Our new planting equipment has superior breakout force, compared to our old machine, which allows us to plant chickpeas to a depth of 200 mm (8″). Planting at this depth delays seedling emergence until after the first week of June, pushing the flowering window back a fortnight, closer to the warmer weather of spring.”

“Chickpea makes a huge difference to our farming system with better wheat yields, less fertiliser and softer soil.”

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Can pulse cover crops tackle multi-resistant ryegrass in irrigated systems?

The best weed control comes from tactics that also bring other benefits to a farming system.
Greg Sefton, principal agronomist with Sefton Agronomics in the Riverina, says multi-resistant annual ryegrass is becoming a major problem in irrigated systems.
Greg Sefton, principal agronomist with Sefton Agronomics in the Riverina, says legume cover cropping is providing effective control of multi-resistant annual ryegrass in irrigated systems.
“Herbicide resistance can move easily through irrigation areas, particularly when the control methods used on the supply channels are limited to just a few herbicides,” he says. “The ryegrass here is generally accepted to have resistance to glyphosate (Group 9 [M]), Group 1 [A] such as clethodim, Group 2 [B] and Group 3 [D], such as trifluralin. Growers are now relying heavily on Group 15 [K] products such as Sakura, and doing their best to rotate out of the problem.”
To regain control, Greg is working with growers to incorporate a multi-purpose fallow crop such as field pea into the system as a winter fallow clean with the added benefit of contributing biological nitrogen into the soil ahead of planting rice or wheat. 
Earlier maturing varieties of field pea provide better weed control options than Kaspa field pea, chickpea and lupin, all of which generally mature later, sometimes after the target weeds have set seed.
“A competitive pulse crop terminated at maximum biomass is an excellent way to reduce weed seed set,” says Greg. “It is a cultural control that also enables the use of some herbicides that are rarely used in our system. Combining the herbicide and cultural methods in the WeedSmart Big 6 is an effective way to keep our cropping options open and to maximise the value of applied water.”

What is the best fit for the legume crop as a winter clean?
In brief: In the Riverina, the optimal place in the rotation is ahead of rice.
The details: Fields selected for rice production are usually bare fallowed for the preceding winter. The aim of the fallow is to control weeds and conserve soil moisture.
Some growers are having success with field pea sown in May as a winter cover crop then terminated for silage or as a brown manure in early September. This fits well with preventing seed set in annual ryegrass, including late germinating plants.
Field pea is a competitive legume and can suppress weed germination and growth when planted in the most competitive configuration possible with minimal soil disturbance and no gaps.
A knockdown treatment of glyphosate (Group 9 [M]), clopyralid (Group 4 [I]) and carfentrazone (Group G [14]) is applied at planting then a mix of pendimethalin (Group 3 [D]), clomazone (Group 13 [Q]) and paraquat (Group 22 [L]) is applied after an irrigation flush to initiate rice germination and prior to rice germination to knockdown both newly emerged barnyard grass (BYG) and persisting ryegrass. This provides a double knock on ryegrass whilst applying a pre-emergent herbicide for barnyard grass in the rice phase.
When implemented once every 4 or 5 years, with a diverse rotation of winter and summer crops in-between, growers can keep a lid on herbicide resistant annual ryegrass populations. 
Field pea is a competitive legume crop that can reduce annual ryegrass germination in the paddock and halt encroachment from the crop borders.
How do you manage weeds on the non-crop areas?
In brief: The same herbicide mix is applied to the whole paddock, including the weeds growing in the check banks.
The details: Weed seed, often carrying herbicide resistance genes, travels easily through irrigation systems and can colonise non-crop areas. Seed from these plants readily infests the cropping areas if not controlled effectively. The control measures used on non-crop zones are often limited to herbicide tactics, so it is important to make sure the herbicide is applied to maximum effect to prevent seed set.
Farm hygiene and physical removal of isolated weeds will also have a positive impact on weed seed production. 
What farming system benefits come with growing a legume cover crop?
In brief: A legume crop grown for biomass rather than grain can improved soil tilth and reduce crusting on some sodic soils. This practice also allows better soil nutrition management and keeps the grower’s options open if the water allocation situation changes.
The details: The field pea crop will fix atmospheric nitrogen and this allows the grower to use 100 to 150 kg/ha less urea to grow the following rice crop without any yield penalty. If there is insufficient irrigation water available for a rice crop, then the fixed nitrogen is still available for a winter crop of canola or wheat.
The phosphorus fertiliser required for rice can be applied when the field pea crop is planted, giving the phosphorus time to become more available in the soil and ready for uptake when the rice is planted.
Field pea is quite drought tolerant, so if irrigation water is not available for rice, the field pea can be grown through to harvest the grain and will usually yield 0.7 t/ha, which can be more profitable than, say, a 1 t/ha drought-affected wheat crop.
Building an integrated farming system based on methods that have multiple benefits is fundamental to staying ahead of weed pressure.
Practical tips for growing field peas as a brown manure crop
Pulses to attack weeds on many fronts


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Rod Birch on how the Big 6 is keeping weeds at bay at Catalina Farms

Catalina Farms is approximately 13,000 ha of 100% cropping, with 65% wheat, with the other 35% comprising of 20% canola and 15% lupins. The longterm rainfall is about 330ml per year and around 250-280ml of growing season rainfall.
Taking on a new property usually has its challenges, but there can be upsides too. Some of the challenges at Koobabbie were related to the fact it had been a livestock property and cropping machinery had never having been run through it. However, Rod explained that they have had some great news about the herbicides they are able to use.
Through the University of Western Australia’s resistance testing service, run by Dr Roberto Busi at AHRI, they found out some older chemistries were still effective, which was a pleasant surprise. Daniel Birch explains below in the Regional Update Podcast what they found out and how they used this information in their planning.

Video breakdown

1:10 Crop rotations – Rod’s favourite rotation is Lupins – wheat – canola – wheat. It provides a lot of diversity for Modes of Action, as well as allows for nitrogen to go back into the soil through the lupin phase.
2:10 Crop Competition – the Birches are big fans of crop competition and it’s an essential part of their approach to controlling weeds.
3:00 Double knock – conditions haven’t been suitable for a double knock since 2016, but when the opportunity arises, it’s an important tool.
4:21 Mix and rotate herbicides – the crop rotations used at Catalina allow for really diverse chemical groups to be used, which is a great tactic to keep resistance at bay.
5:52 Stopping weed seed set – the Birches are trying to eliminate as many weeds in the crop as possible. Crop topping is a tool that they employ, as well as late spraying where necessary.
6:49 Harvest weed seed control – seed destruction is on the horizon at Catalina, but logistically has been a bit tricky.
7:21 Acquiring Koobabbie – it has been exciting for the Birches to be able to introduce more diverse rotations. They’ve been able to use Modes of Action which have never been used before.
9:48 Soil amelioration  – liming has been a really beneficial tool for Catalina Farms. They also put out pot ash and gypsum. Deep ripping has also been a great tool to remove the compaction layer.
11:29 Big 6 benefits  – controlling weeds is such an important strategy at Catalina Farms. Rod Birch said “We’ll never have a ceasefire on the war on weeds!”.


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