Read time: 4 minutes

Kohlhagen family is keeping weed numbers low

A changed attitude to weeds has been driving brothers Malcolm and Des Kohlhagen to implement a comprehensive management program on their farm near Wagga Wagga in southern NSW.

Fifteen years ago the Kohlhagens assessed their weeds in terms of their likely economic impact but their mindset has changed to a much lower tolerance of weeds and they aim to keep numbers low year in, year out.

Brothers Malcolm and Des Kohlhagen along with Malcolm’s son, Adrian who has recently returned to the farm, have developed and implemented a comprehensive weed management program for their 100 per cent cropping operation in southern NSW.

Brothers Malcolm (left) and Des (rear) Kohlhagen along with Malcolm’s son, Adrian (centre), have developed and implemented a comprehensive weed management program for their 100 per cent cropping operation in southern NSW.

The sheep have all gone from their 1600 ha operation and the family has expanded their cropping program to include a wider range of crops. The winter program now includes wheat, barley, canola, albus lupin and, most recently, faba bean.

Malcolm and Des use break crops to introduce a different range of herbicides into the rotation and a double break of a pulse followed with canola provides two years of grass control so the cereals are sown into clean paddocks. The Kohlhagens have stuck to their crop rotation even when many other growers in the district reduced their canola hectares during the 2000s.

They grew field peas many years ago but gave them away due to harvesting difficulties, and now find lupin and faba bean are a better fit in the rotation, providing a definite nitrogen boost for the following canola crop.

Triazine tolerant (TT) and Clearfield canola are used to rotate chemical modes of action. The Kohlhagens don’t currently consider RoundUp Ready canola an option for them due to delivery point and marketing issues.

Harvesting weed seed

Canola crops are windrowed to aid in harvest management and, from this season, will be crop topped under the cutter bar to capture any late escaping weeds. The Kohlhagens also plan to crop top their pulse crops in years where late escapes are a problem.

A narrow windrow chute is used on the harvester to collect weed seed in the pulse and canola crops and the narrow windrows are burnt to kill any seed present. This means over 40 per cent of their cropping area is subject to this very effective non-herbicide weed control method, particularly for annual ryegrass.

A double break crop of a pulse crop followed with canola provides excellent grass weed control, including narrow windrow burning, before returning to cereals in the rotation.

A double break crop of a pulse crop followed with canola provides excellent grass weed control, including narrow windrow burning, before returning to cereals in the rotation.

The brothers do not narrow windrow burn their cereal crops because of the high stubble load from barley and wheat crops yielding up to 6.5 t/ha and 5 t/ha respectively. When grown back to back these cereal crops generate too much stubble to effectively confine the fire to the narrow windrows.

Getting the right conditions for burning is not always easy but the Kohlhagens believe it is worth doing and are looking forward to when they can justify investing in an integrated Harrington Seed Destructor so they can avoid burning, a practice that is not popular in town!

In years where weed populations increase for any reason, haymaking is an effective method to stop weed seed set. The Kohlhagens find their heavier soil types are more likely to be challenged with weed blow-outs so they target these areas for haymaking as a salvage operation when necessary, giving great weed management benefits in poorer seasons.

Malcolm and Des currently contend with ryegrass that is resistant to Hoegrass (Group A, fop) and are aware of similar resistance arising in wild oats and possibly wild radish on the farm. To keep wild radish numbers as low as possible they hand rogue plants in spring, to avoid any seed going through the header.

Competitive cropping

Further narrowing their row spacing to create greater crop competition is currently on the table for the family but until they have decided on the best option they are using high seeding rates, especially in the already-competitive barley crops. Blockages in the seeder and slug and slater damage to seedlings can create gaps in the rows, which provides the opportunity for weeds to flourish, and wider rows also allow more weeds to grow between rows.

Changing the seeding setup is quite an expense so the family is considering whether to reduce the spacing on their current tined seeder to 250 mm or to change to a disc seeder.

Even at 300 mm they are having trouble managing the stubble load so are hesitant to narrow the spacing much further, however the tined seeder allows them more herbicide options than can be safely used with disc seeders. On the other hand, they have been impressed with a 150 mm disc seeder they have seen operating in high stubble environments in South Australia.

When the Kohlhagens first moved to controlled traffic, wheel tracks were left bare.  However, the gap left by the wheel tracks in the controlled traffic system lets more light into the adjacent rows, allowing more weeds to establish. To reduce this effect the Kohlhagens now seed their wheel tracks using a mid-row banding disc to provide increased crop competition and reduce weeds.

Residual herbicides

Pre-emergent herbicides are applied in all crops for grass control. While clethodim is still providing effective control in canola the Kohlhagens are well aware that it may not continue to be an option in the future. To support the pre-emergent herbicides the Kohlhagens are sowing their canola and pulse crops early to encourage better establishment and more rapid canopy closure, reducing the opportunity for in-crop weed germinations after the residual effect has diminished.

Changed farming system; changed weed spectrum

Since moving from a mixed farming operation to 100 per cent cropping, Malcolm and Des have seen a change in the weed spectrum present on the farm, with less capeweed present and less movement of weed seed around the farm.

Not having livestock however has increased the need for more vigilance over summer to prevent weeds using precious soil moisture that may be the difference between finishing a crop and crop failure as the October rainfall is now less reliable. Fleabane is of particular concern in summers with higher rainfall seeing explosions in fleabane populations, which may require double knock treatments.

Hairy panic is another persistent weed that must be sprayed when small to achieve effective and economical control. To manage broadleaf weeds the Kohlhagens use a low volatile 2,4D ester spike in glyphosate sprays applied over summer. Milk thistle is another emerging weed that is taking advantage of the no-till farming system.

Clean seed a priority

Prior to harvest Malcolm and Des inspect their paddocks to identify the cleanest areas of each variety suitable to harvest for retained seed. They then use a low capacity seed grader to remove small or damaged seed and as much weed seed as possible from their seed before storing on-farm.

A mobile grader is contracted to grade the pulse grain for marketing and to thoroughly clean the pulse seed retained for sowing.

Malcolm and Des are clearly on top of their game with their weed management program but they are also full of praise for their agronomist, Greg Condon from Grassroots Agronomy, who provides excellent agronomic advice and keeps their herbicide program up to date.



Related Articles

View all
Article
News

WeedSmart agronomist set to tackle high rainfall zone weeds

Every locality has its own spectrum of weeds, and growers face different opportunities and challenges regarding the control tactics they can employ. The WeedSmart Big 6 approach is a practical way to ensure that an integrated weed management program is put in place that disrupts weed seed production and the evolution of herbicide resistance. Commencing in January 2021, Jana Dixon has joined the WeedSmart team of extension agronomists, with a focus on applying the Big 6 to manage weeds in the high rainfall cropping systems of southern Australia – from Esperance in WA to south-eastern SA, Tasmania and south-western Victoria. Jana will add to the dedicated and experienced extension agronomists on the WeedSmart team with Peter Newman in the Western region, Chris Davey in the South, Greg and Kirrily Condon in the East and Paul McIntosh in the North. Jana Dixon has joined the WeedSmart team of extension agronomists, with a focus on applying the Big 6 to manage weeds in the high rainfall cropping systems of southern Australia – from Esperance in WA to south-eastern SA, Tasmania and south-western Victoria. Jana hails from the Mid North of SA, and began working at Pinion Advisory (previously Rural Directions) while she was studying agriculture at the University of Adelaide. She has been employed full-time at Pinion Advisory since January 2019 as an agribusiness consultant, based in Clare, and spends most of her time delivering agronomy and farm business advice to clients from a wide range of cropping regions in South Australia. Pinion Advisory is a foundation WeedSmart sponsor and Jana has been involved in two WeedSmart Week events already – the first as a participant and grower group organiser at the Horsham event in 2019 and then as the local organiser for WeedSmart Week 2020 in Clare. In welcoming her to the WeedSmart team, program manager Lisa Mayer says Jana brings energy, commitment and insight to deliver communications focussed on the southern region’s high rainfall regions. “Growers in the southern high rainfall zones are facing some serious issues with herbicide resistance influencing their farming decisions,” says Ms Mayer. “Jana will be engaging with agronomists, growers and researchers in each of the distinct high rainfall zones to understand the complexities and look for practical ways to apply the WeedSmart Big 6 in various cropping scenarios.” “We plan to deliver WeedSmart Week in Esperance, part of Western Australia’s high rainfall cropping zone, in August 2021 and Jana will play a key role in the planning and delivering of our annual 3-day flagship event.” Jana says her experience with the WeedSmart program has been very positive and she has been particularly impressed with the support the program has from all sectors of the grains industry. Newly appointed WeedSmart extension agronomist, Jana Dixon (green cap) leading discussions with farm visit host, Ben Marshman, Owen SA, and growers and agronomists attending WeedSmart Week 2020 in Clare. “I have spoken to many growers and agronomists who have found real value in the information that the WeedSmart program delivers,” she says. “For many it is as much about considering another operator’s philosophy on dealing with weeds, and taking a fresh look at their own systems, rather than just learning about a new tactic or the traits of a new herbicide in isolation from the big picture.” She says the high calibre of industry people who contribute their time and expertise to the program is testament to the value WeedSmart has to agribusiness, growers, agronomists and researchers alike. In taking on the responsibility for delivering information tailored for the high rainfall zones Jana says she is pleased to have an extensive network of contacts through Pinion Advisory, with offices in a number of high rainfall areas to provide easy access to local agronomists and growers. She is also aware that there are major differences in weed spectrums and farming systems in each high rainfall zone and plans to take full advantage of the opportunity this role presents to expand her understanding of different approaches to weed management. “The long and favourable growing season and the associated prolonged periods of weed germination, is a key factor that I see potentially impacting on a grower’s weed management strategies in these regions,” she says. “On the other hand, access to highly diverse rotations and a focus on crop competition are two strategies that can play an important role in achieving excellent weed management in these regions.” “I am keen to engage with anyone working and farming in the high rainfall zones to build my knowledge and understanding,” she says. “And to create opportunities to develop and extend the WeedSmart Big 6 strategies, both herbicide and non-herbicide, that work in each area and in different situations.” WeedSmart is the industry voice delivering science-backed weed control solutions with support from the Grains Research and Development Corporation (GRDC), major herbicide, machinery and seed companies, and university and government research partners, all of whom have a stake in sustainable farming systems. You an follow Jana on Twitter and keep up to date with the HRZ here.
Article
News

Never cut the herbicide application rate

Scientific studies have demonstrated that resistance can rapidly evolve in weeds subjected to low doses of herbicide. Some weeds can develop resistance within a few generations. Full rates when mixing herbicides too! When mixing herbicides it is important that each product is still applied at the full label rate to ensure high mortality. Applying different chemicals in one mix can provide an additive advantage. It is important to understand the mode of action of each herbicide on the plant when preparing a herbicide mix. This is just as important for pre-emergent grass weed mixes as it is for post-emergent mixes aimed at broadleaf weed control. ALWAYS READ THE LABEL. Surrounding weed seeds with a combination of pre-emergent herbicides with different modes of action can give a high level of control and help extend the useful life of all the chemicals used. The high level of control must be supported with additional control measures for all survivors. All products with different modes of action must be applied at full label rates for this to be an effective strategy.   Mixing two chemicals with the same mode of action can achieve some additional efficacy, however, the mix should deliver the combined full rate to ensure a lethal dose. The amount of stubble present and crop safety are all important considerations when mixing chemicals. For example, when using a tank mix of Avadex® and trifluralin to control ryegrass in wheat, the rates used will vary depending on the sowing system and level of stubble retention. Be sure to get good advice. Many herbicides on the market are a combination of two or more modes of action within the one product. These products must be applied at the full label rate to be effective. Having dual action does not negate the need to change herbicide products and rotate modes of action. Repeated use of any single strategy will reduce the effectiveness of that strategy over time.  
Article
News

Spray well – correct nozzles, adjuvants and water rates

Spray application is a technical field and growers need to make sure their equipment and application techniques are spot-on. The GRDC Spray Application GrowNote provides detailed information and about 80 videos to demonstrate key skills. Prevent spray-drift The focus of spraying herbicide needs to be on doing the job right so the weeds receive the correct dose and die, and this includes reducing the air borne fraction to a bare minimum. Bill Gordon’s 10 Tips for Reducing Spray Drift Choose all products in the tank mix carefully. Understand the product mode of action and coverage requirements. Select (and check) the coarsest spray quality that will provide effective control. Expect that surface temperature inversions will form as sunset approaches and will likely persist overnight and even beyond sunrise on many occasions. DO NOT SPRAY. Use weather forecasts to inform your spray decisions. Only start spraying when the sun is about 20 degrees above the horizon and when the wind speed has been above 4–5 km/hr for more than 20–30 minutes, and clearly blowing away from any adjacent sensitive crops or areas. Set the boom height to achieve a double overlap of the spray patterns. Avoid higher spraying speeds. Leave buffers unsprayed if necessary and come back. Continue to monitor conditions, particularly wind speed, at the site during the spray operation High water rates don’t have to slow you down Some growers are concerned that increasing the water rate when applying herbicide will slow down their spray operation and cost them money. However, the biggest financial loss during spraying usually comes from a failed spray job. To keep your spray operation as time efficient as possible when using more effective and reliable application volumes, you can: Use nurse tanks around the farm to reduce the time spent travelling back to a central re-fill point. Use a larger pump, e.g. 2.5 inch, to make re-filling quicker. Pre-mix the batch while the sprayer is operating. Many mixes can be held in the mixing tank for up to 6 hours. However, wettable granules and suspension concentrates will need agitation to keep them in solution. For pre-emergent herbicides in high stubble situations, carrier volume has a large effect on the level of control achieved. Across four trial sites Dr Borger’s research demonstrated that ryegrass control with trifluralin or Sakura® increased from 53% control when the carrier volume was 30 L/ha to 78% control when the carrier volume was increased to 150 L water/ha in high Water quality and mixing order Water quality is often overlooked as a possible contributor to herbicide failure and can lead to confusion over the herbicide resistance status of weeds on a property. Water should be considered as one of the chemicals in any mix, given that water quality varies markedly depending on its source. Getting the mixing order right is essential for effective spray results. Don’t start mixing until the water quality is right Podcast – Mixing herbicides Adjuvants Sometimes adding an adjuvant is beneficial and sometimes it is detrimental; and there is an art to knowing how to best deploy these additives. When weeds are susceptible to the applied herbicides, the effectiveness of adjuvants generally goes un-noticed. Correctly applied adjuvants can reduce the impact of low level herbicide resistance by helping to maximise the amount of herbicide taken up by the plant.

Subscribe to the WeedSmart Newsletter