Crop competition

Help your crops win the war against weeds by increasing their competitiveness against them.

We don’t want to give the weeds a free kick by growing un-competitive crops. Crop competition with weeds is a double-edged sword. There is the effect of the weeds on the crop, and the effect of the crop on the weeds. A competitive crop will suffer less yield loss at the hands of the weeds, and will also reduce seed set of the weeds compared to an un-competitive crop. In other words more crop, fewer weeds.

There are six main aspects of crop competition:

  1. Higher seeding rate
  2. Narrow row spacing
  3. Orientation of crop – a crop sown east – west will give your crop enough sunlight, and shade the furrows to starve weeds of sunlight.
  4. Vigorous crop traits
  5. Soil health – give your crop the best chance by having healthy soil
  6. Time of sowing – early sowing is usually best

It’s hard to get all of the six points above right, and growers need not aspire to practising all six of these competition factors, but they can use a range of these practices to ensure that their crops have a fighting chance against the weeds.

You can learn more about crop competition in our Diversity Era course, Crop Competition 101 – take a look here.

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Crop competition – give your crops the edge

The uncomfortable truth is that in many paddocks the weeds are winning the battles for space and resources. Growing crops that out-compete weeds gives a double whammy benefit of more crop and less weeds — generating more profit! Try some or all of these ideas to give your cropping system the competitive advantage: Get the soil pH right and do what you can to improve overall crop nutrition Set up your planter to sow crops on the narrowest row configuration possible within the other constraints of crop production Sow within the optimal planting window for the crop and your location Choose the most competitive crop type (e.g. barley over wheat) and the most competitive variety or hybrid of your chosen crop Select crops with early vigorous growth Set the crop up for success with optimal weed control prior to planting, using double knock tactics and effective pre-emergent herbicides Sow east-west rather than north-south if you can Use sowing rates at the upper end of the recommended range for the crop And here’s more advice from the WeedSmart crop competition experts: Can planting a tight crop improve weed control? Use your crop as a weapon Using your crop to fight weeds Webinar with Prof Deirdre Lemerle: Using your crop to fight weeds  Up the competition Employ crop competitiveness to combat weeds Higher seeding rates lower weeds  Narrow row spacing: is it worth going back? AHRI insight: Sow west young man AHRI insight: Left jab, right hook AHRI insight: Heal thy soil, heal thy crops, kill thy weeds
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Article

Spray drift & crop competition

Join your hosts Jessica Strauss and Peter Newman in the first podcast for March! Spraying weeds and choosing seeds are the hot topics this podcast. We chat with Nufarm Australia Spray Application Specialist Bill Gordon, who gives some great tips and insights on correct set-up. Rohan Brill also joins us for insight on choosing canola seeds and the benefits of crop competition! Our webinar series is also kicking off for 2017 next week! If you’d like to register for the March 7 webinar with Rohan Brill, who will be going into more detail on crop competition, click here!
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Ask an Expert

Does delayed sowing help manage weed populations?

with Dr Gurjeet Gill, Associate Professor – Weed & Crop Ecology, University of Adelaide The answer to this question is a very simple ‘no’. Waiting for weed seeds with longer dormancy to germinate before sowing costs yield and weeds often set more seed in late sown crops.   Dr Gurjeet Gill, Associate Professor of Weed and Crop Ecology at The University of Adelaide says sowing a competitive crop ‘on time’ has better outcomes for both crop yield and suppressing weed seed production. Dr Gurjeet Gill, Associate Professor of Weed and Crop Ecology at The University of Adelaide is one of the four experts presenting the new WeedSmart Crop Competition 101 online course. “The lack of effective in-crop herbicides leaves growers with few chemical options when it comes to controlling weeds like annual ryegrass and brome grass that are emerging later in the crop,” says Gurjeet. “Our field trials in South Australia demonstrated that sowing ‘on time’ is the best way to maximise crop yield and suppress weeds that germinate in-crop, both with and without the use of pre-emergent herbicides.” The time of sowing x seeding rate x herbicide field trials were conducted at several sites in South Australia in 2018 and 2019 with GRDC investment. “The other aspect of these trials was investigating the effect of seeding rate on weed density and seedhead production,” says Gurjeet, “Higher seeding rate increased the yield in wheat at Minnipa at both times of sowing, and did not increase screenings.” Early sown crops consistently produce more crop and less weeds. Dr Gill is one of the presenters in WeedSmart’s new Diversity Era ‘Crop Competition 101’ course, which can be completed online in less than 10 hours, giving you a solid grounding in ways to effectively implement tactics that give crops a competitive advantage over weeds. This free online course can be found at www.diversityera.com/courses/crop-competition-101 Why are weeds in cropping systems becoming more dormant? Short answer: Increased cropping intensity and routine use of pre-emergent herbicides selects for the longer dormancy trait in annual ryegrass and brome grass. Longer answer: Weed populations have a mix of individuals with different levels of seed dormancy. In self-regenerating pastures, there is likely to be a penalty for high seed dormancy and germinating later than the neighbouring plants. Therefore, high dormancy late germinating plants remain a minority in the population. However, the situation changes when growers switch to intensive cropping where knockdown herbicides routinely kill the very early germinating plants. In such systems, weeds that emerge with or soon after the crop have a greater survival because they escape the effects of the knockdown herbicides. After several years of cropping, weed populations change from being early germinating to later germinating. These later germinating weed populations are less responsive to delayed sowing and are now common in southern farming systems. See the seed dormancy explainer below for more information on the mechanisms at play. How can I reduce the impact of these late-emerging ryegrass and brome grass weeds? Short answer: Grow the most competitive crop possible – cultivar, seeding rate, row spacing, row orientation and time of sowing all have an impact. Longer answer: In these trials, time of sowing was by far the major contributor to weed suppression and crop yield – even when no pre-emergent herbicide was applied. Delaying sowing to wait for weeds to germinate after breaking rain is usually counter-productive, unless the delay results in better soil moisture conditions for pre-emergent herbicides. But even when there is a weed control benefit from the later sowing date there is likely to be a penalty on crop yield of at least 20 per cent. This was demonstrated at the Minnipa site in 2018, where a delay in sowing of wheat reduced in-crop ryegrass density and its seed production, but there was a yield penalty of 25 to 43 per cent. Also in 2018, the delayed sowing treatment at Marrabel, saw a large reduction in brome grass plant density in barley — however, weed seed production on these fewer plants was high. Delayed seeding also reduced barley grain yield by almost 30 per cent. In barley, the additional in-crop use of Intervix completely prevented weed seed set at both the on-time and delayed time of sowing. As resistance to Intervix is still quite rare in brome grass, use of Clearfield® crops can be a highly effective part of the management program. Field trials at various locations across South Australia clearly demonstrated that sowing a competitive crop ‘on time’ has better outcomes for both crop yield and suppressing seed production on annual ryegrass and brome grass. Photo: University of Adelaide.   What is the effect of seeding rate? Short answer: Higher crop seeding rate can greatly reduce weed seed production. Longer answer: In these trials, doubling the crop seeding rate from 100 to 200 plants per m2 usually reduced weed seed production by 30 to 40 per cent. In the barley trial, the performance of the late planted crop was improved when the higher seeding rate was used. In many other trials, very high seeding rates (such as 400 plants per m2) have been shown to vastly reduce annual ryegrass numbers. Using variable rate seeding, growers can consider sowing known weedy patches at very high seed rates (e.g. 250 to 300 plants per m2) simply to outcompete weeds. Using a sowing rate at the upper end of the recommended range for the chosen cultivar is good practice to help support the efficacy of pre-emergent herbicides early in the season and provide strong competition for weeds that emerge later in the season. Seed dormancy explainer  Seed dormancy is usually associated with a ‘dark’ requirement, where seeds can remain dormant on the surface, where they are exposed to light, but when they are ‘planted’ the dark requirement is filled and germination follows. These weeds are the target of pre-emergent herbicides in no-till farming systems. What growers have observed, and researchers have tested, is that some weeds remain dormant even after the dark requirement has been fulfilled, suggesting that some other trigger may be at play. In brome grass, for example, it has been demonstrated that some seeds do not germinate until a ‘cold requirement’ has been fulfilled. These weed seeds remain dormant in the soil until the night temperature reaches 4 degrees C, often well after any pre-emergent herbicide applied at seeding has degraded. Once the weeds with the cold dormancy trait have established and set seed they can become the dominant in-crop weed pressure to impact crop yield, and future applications of pre-emergent herbicides will have a limited effect on the population.
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Case Study

Stephen and Michelle Hatty, Matong NSW

The family now crops a total 2100 ha of land within an 11 km radius, on a very flat landscape with soils ranging from red loam to heavy red clay and self-mulching black clay. They adopted reduced tillage practices in the 1990s and now run a 12 m controlled traffic farming (CTF) system.   The Hatty family uses a double break crop sequence strategy of a pulse then canola, followed by wheat then barley to put firm downward pressure on the weed seed bank. The very wet season in 2016 resulted in unavoidable soil compaction and weed escapes, which prompted Stephen and Michelle to upgrade from a tyne seeder on 333 mm rows to an NDF disc seeder on 250 mm rows. The seeder has worked well from the first season onwards with dry sown crops establishing uniformly since 2017. “We had been considering the change for a while as disc seeders work well in heavy clay soils, conserve more moisture and result in much less soil disturbance,” says Stephen. “We had been finding that even though the soil structure is quite good, the tyne seeder tended to bring clods to the surface when the soil is dry at the start of the canola seeding program in April.” “It also gave us the opportunity to further increase crop competition with the narrower rows,” he says. “We also get better seedbed utilisation and can lift our planting rates to maximise yield.” Changing to a disc seeder gave the Hattys the opportunity to further increase crop competition with the narrower rows and lift their planting rates to maximise yield and optimise seedbed utilisation. The Hattys use a double break crop sequence strategy of a pulse then canola, followed by wheat then barley to put firm downward pressure on the weed seed bank. Stephen says the pulse phase of faba beans, lentils or field peas helps improve subsoil moisture and soil nitrogen for the following canola crop. Pulses offer different chemistry options for grass weeds and even brown manuring if weed pressure is high. “For example, trifluralin is normally out for cereals but can be used after a pulse crop like faba beans that doesn’t leave much cover on the paddock,” he says. “We also use water rates of 80 to 100 L/ha to maximise the effectiveness of pre-emergent herbicides in high stubble situations.” The Hattys are keen to host trials on their property where they are able to see first-hand the outcome of different agronomic options or crop performance. In 2017, they hosted NSW DPI trials looking at the competitive ability of Planet and La Trobe barley, with Planet being more prostrate in growth habit and La Trobe being very upright. In 2017, they hosted NSW DPI trials looking at the competitive ability of Planet and La Trobe barley, with Planet being more prostrate in growth habit and La Trobe being very upright. “We sow all our crops early in their optimal sowing windows and try to take advantage of more competitive varieties to suppress weed growth,” says Stephen. “In dry conditions barley is a great option to reduce weeds, produce significantly higher grain yield and return more straw than wheat ahead of sowing a pulse crop.” In 2015 the Hattys added harvest weed seed control to the program. They chose to fit an Emar chaff deck system to their Case 8230 header and have been confining weed seed to the 3 m tramlines ever since. Since adding an Emar chaff deck system to their Case 8230 header in 2015 the Hattys have slowed down the chaff deck conveyors and added a chopper to improve straw spreading. “We have slowed down the chaff deck conveyors and added a chopper to improve straw spreading,” says Stephen. “We had already been harvesting fairly low to suit the tyne seeder so there was no real change to the way we harvest. As time goes on we expect that less and less weed seed will be deposited each harvest resulting in fewer and fewer weeds growing on the tramlines.”

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Weather forecast accuracy and crop competition trial results

This week on the podcast, we look into how to utilise weather forecasts and get the latest information on crop competition trials conducted by YP AG. Agriculture Victoria Seasonal Risk Agronomist Dale Grey provides an excellent overview of what weather forecasts to take seriously and those which you should probably take with a grain of salt. Dale has a real knack for simplifying this complicated topic, so if you want to get a good overview of the weather, he’s your man! Dale refers to no breaking rains yet in the interview but since the interview, there have been some breaking rains across parts of southeast Australia. You can check out the latest map for May rain thus far here. Also on related climate topics, the ‘Climatedogs’  🐶 🦴 animations (key climate drivers) were updated for a national audience recently and you can check them out here. And if you’d like to keep up-to-date with all of Dale’s weather forecasting, you can simply hit a button to subscribe to The Break here. We’re also excited to have Agriservices Agronomist Chris Davey (pictured up top) on this podcast talking about crop competition at seeding time. Chris is based in Kadina, South Australia and he recently wrote a great article in YP AG’s agronomy newsletter, where he said ‘weed seed reduction starts at seeding’. There are multiple benefits of crop competition, including increasing crop yield in weedy situations, reducing weed seed set, and improving the efficacy of Harvest Weed Seed Control. Chris has kindly given us access to his article if you’d like to refer back to it after the interview on the results from YP AG’s recent trials and some tips on crop competition. You can download it here. You can find out more about YP AG here. Join your hosts Jessica Strauss and Peter Newman and…  
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Podcast

Disc seeding systems

Nearly a year ago, WeedSmart Extension Officer Greg Condon co-hosted a podcast with Jessica Strauss on disc seeding and stripper front systems. It’s a bit more of an obscure system, but it sure generated a lot of interest and is currently our most played episode, with more than 750 listens (you can check it out here). Given the interest, we thought we’d put together another podcast of similar ilk, but this time focusing on disc seeding itself. In this podcast, you’ll hear from Murry Scholz. He’s based in Henty, NSW and has a John Deere, with a disc seeder on 7.5” rows. He’s a mixed farmer and 2017 was his first year using the disc seeder. You may already be familiar with the Hatty family as they hosted growers on their farm for WeedSmart Week in 2017 and have been featured in podcasts and stories through WeedSmart. In this podcast, Stephen Hatty gives us some insight into his disc seeding operation. Stephen is based in Matong, NSW and has an NDF disc on 10” rows, on heavy clay soils. Like Murray, 2017 was the first year he used the disc seeding system.   Murray Scholz This picture shows Murray’s John Deere single disc unit.   Even crop establishment between two different wheat varieties and wheat maturity on 7.5 inch rows at Murray’s farm in 2017 (disc seeding). Stephen Hatty Stephen Hatty, with his father Rodney Hatty.   Stephen Hatty’s NDF disc unit up close.  

Case Studies

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Case Study

Stephen and Michelle Hatty, Matong NSW

The family now crops a total 2100 ha of land within an 11 km radius, on a very flat landscape with soils ranging from red loam to heavy red clay and self-mulching black clay. They adopted reduced tillage practices in the 1990s and now run a 12 m controlled traffic farming (CTF) system.   The Hatty family uses a double break crop sequence strategy of a pulse then canola, followed by wheat then barley to put firm downward pressure on the weed seed bank. The very wet season in 2016 resulted in unavoidable soil compaction and weed escapes, which prompted Stephen and Michelle to upgrade from a tyne seeder on 333 mm rows to an NDF disc seeder on 250 mm rows. The seeder has worked well from the first season onwards with dry sown crops establishing uniformly since 2017. “We had been considering the change for a while as disc seeders work well in heavy clay soils, conserve more moisture and result in much less soil disturbance,” says Stephen. “We had been finding that even though the soil structure is quite good, the tyne seeder tended to bring clods to the surface when the soil is dry at the start of the canola seeding program in April.” “It also gave us the opportunity to further increase crop competition with the narrower rows,” he says. “We also get better seedbed utilisation and can lift our planting rates to maximise yield.” Changing to a disc seeder gave the Hattys the opportunity to further increase crop competition with the narrower rows and lift their planting rates to maximise yield and optimise seedbed utilisation. The Hattys use a double break crop sequence strategy of a pulse then canola, followed by wheat then barley to put firm downward pressure on the weed seed bank. Stephen says the pulse phase of faba beans, lentils or field peas helps improve subsoil moisture and soil nitrogen for the following canola crop. Pulses offer different chemistry options for grass weeds and even brown manuring if weed pressure is high. “For example, trifluralin is normally out for cereals but can be used after a pulse crop like faba beans that doesn’t leave much cover on the paddock,” he says. “We also use water rates of 80 to 100 L/ha to maximise the effectiveness of pre-emergent herbicides in high stubble situations.” The Hattys are keen to host trials on their property where they are able to see first-hand the outcome of different agronomic options or crop performance. In 2017, they hosted NSW DPI trials looking at the competitive ability of Planet and La Trobe barley, with Planet being more prostrate in growth habit and La Trobe being very upright. In 2017, they hosted NSW DPI trials looking at the competitive ability of Planet and La Trobe barley, with Planet being more prostrate in growth habit and La Trobe being very upright. “We sow all our crops early in their optimal sowing windows and try to take advantage of more competitive varieties to suppress weed growth,” says Stephen. “In dry conditions barley is a great option to reduce weeds, produce significantly higher grain yield and return more straw than wheat ahead of sowing a pulse crop.” In 2015 the Hattys added harvest weed seed control to the program. They chose to fit an Emar chaff deck system to their Case 8230 header and have been confining weed seed to the 3 m tramlines ever since. Since adding an Emar chaff deck system to their Case 8230 header in 2015 the Hattys have slowed down the chaff deck conveyors and added a chopper to improve straw spreading. “We have slowed down the chaff deck conveyors and added a chopper to improve straw spreading,” says Stephen. “We had already been harvesting fairly low to suit the tyne seeder so there was no real change to the way we harvest. As time goes on we expect that less and less weed seed will be deposited each harvest resulting in fewer and fewer weeds growing on the tramlines.”
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Case Study

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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Case Study

Bruce family, Alford SA

Keeping pressure on brome grass with HWSC Brothers Gary, Paul and Bronte Bruce farm at Alford on the Yorke Peninsula, SA have used harvest weed seed capture as an important tool in their weed management program to bring down grass weed numbers in their continuous cropping business. For the last 15 to 20 years the Bruce family has followed a 3-year rotation of wheat – barley – legume, having exchanged field peas for lentils in the legume phase in recent years. They found that producing export hay on grassy paddocks was a very effective way to manage grass weed seedbank, to the point where they had only one paddock of hay in 2016 and no hay in 2017. Gary Bruce, together with the family’s agronomist Chris Davey, YP-AG sets out a plan for the season, including our weed management program, with different strategies used depending on whether there is a wet or a dry start. “Hay production is hard work and now that we don’t have much of a grass weed problem we are taking hay out of the rotation for a while,” says Gary. “The hard work was certainly worth it in terms of regaining control over herbicide resistant weeds on the farm. Now we’d like to keep more crop residue on the paddocks to improve the hardsetting nature of the soil here.” Having used a chaff cart for many years, the Bruce’s were well aware of the benefits of capturing weed seed in the chaff stream but Gary was very interested to hear HWSC advocate and WA grower, Ray Harrington, speak at a field day about chaff lining. In 2017 harvest they used chaff line chutes on two headers for the first time. As usual they learnt a lot in their first harvest and have plans to make even better use of the system this season. Gary is very aware of the fact that there is very limited research on the long-term impact of chaff lining on weed management. “Our farm is partially set up for controlled traffic with 12 m and 36 m gear so the chaff line ends up on a spray track every third run,” he says. “We found starting the harvester on a spray track at the edge makes the best use of the wheeltracks. If we go to a full CTF system we will probably change to using a chaff deck system but the chaff lining chute is certainly a cheap and effective way to confine weeds to a small area of the paddock while also retaining the stubble.” Gary’s farm is partially set up for controlled traffic with 12 m and 36 m gear so the chaff line ends up on a spray track every third run. So far they have found using the chaff lining chute is a cheap and effective way to confine weeds to a small area of the paddock while also retaining the stubble. HWSC and late germination Brome grass is the most problematic weed on the Bruce’s farm with limited options for control in the cereal phase. There are limited chemical control options to kill early germinating brome grass before seeding and so Gary relies on HWSC to take care of late germinating cohorts. They recognise that hay making has played an important part in keeping this weed in check and acknowledge this could be more difficult if they get out of hay production altogether. All crops are sown to achieve greatest crop competition possible using 25 cm row spacing and cultivars that are well suited to the different soil types. Two-thirds of the farm is inter-row sown while paddocks with hardsetting topsoil generally follow the same furrow as the previous year. As the soil improves through increased residue retention Gary hopes most of the farm will eventually be sown in the inter-row. Generally they find, Scepter wheat yields better than Mace, Compass barley produces the most straw, PBA Bolt lentils give salt and boron tolerance where it’s needed and PBA Hurricane lentils offer Group B herbicide tolerance. “Early in April we usually speak with our agronomist, Chris Davey, about a plan for the season, including our weed management program,” says Gary. “For example, wet and dry starts need different strategies such as ensuring there is sufficient moisture to activate metribuzin and propyzamide before sowing lentils. We have also experienced more summer rainfall recently and often need to do two sprays for summer weed control.” Other resources: Implementing the WeedSmart Big 6 on the Yorke Peninsula
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Case Study

Edwards family, Port Broughton SA

Stacking weed control tactics for maximum effect Farming on the sand hill swales near Port Broughton on the Yorke Peninsula, Pete Edwards is doing everything in his power to stop herbicide resistance in brome grass and wild radish. “We take a zero tolerance approach to escapes, particularly with brome grass, and have used a chemical fallow in areas with high brome numbers,” he says. “It’s a case of ‘short term pain for long term gain’ and even after a chemical fallow we will chase any survivors by hand rouging or spot sprayer. Keeping on top of brome survivors has certainly paid off and we have seen numbers decline.” L-R: Tim Edwards, Chris Davey (YP-AG) and Peter Edwards. Chaff carts have served a purpose but their time on the Edwards’ farm is limited and this harvest they will most likely introduce a chaff deck system to replace the chaff cart. In wheat Pete has had good results with non-imi chemicals such as Avadex + Sakura and Avadex + Boxer Gold, in conjunction with narrow windrow burning, which helps manage the stubble and maximises the efficacy of these more expensive herbicides. “There are very few options for wheat so it is essential that we keep pressure on brome numbers in our other crops and also give the group B herbicides a rest to help preserve the imi-tolerant crop options,” he says. “We are only a few applications away from serious resistance issues with fop and dim chemistry. When patches of weeds are not killed by our normal herbicide applications we go back and apply high rates of clethodim to achieve 95 per cent kill, and then go back again to hand rogue any survivors.” Pete is also mixing fops and dims such as Select, Verdict and Factor and the Intervix brew to extend the life of these modes of action. He has seen the value of including adjuvants such as Supercharge for Factor and ammonium sulfate to maximise the impact on hard-to-kill brome grass. The Edwards have installed a digital weather station on their farm that also provides local data to ten other growers who subscribe to access the data. Having access to local, real-time weather information, including automated Delta T calculations, means that Pete and his neighbours can avoid frosty and dewy conditions and minimise spray drift, making every application as effective as possible. When collecting seed for herbicide testing Pete looks specifically for plants that are stunted or deformed as they are likely to be indicator individuals of what might be happening in the paddock and the results help him to plan ahead with chemical choices. The Edwards family have used chaff carts for 12 years and through extensive testing have proven that operating at a slower speed really does capture more weed seed. Rather than dropping small chaff piles across the paddocks the Edwards build large chaff dumps about 200 m apart. In addition to the chaff cart, Pete has designed a narrow windrow chaff management system of his own that drops the straw on the ground and places the chaff on top. “We did conventional narrow windrow burning 10 to 15 years ago and had several years where the windrows got wet and didn’t burn the weed seeds effectively,” he says. “Putting the chaff on the top of the narrow windrow means that even if they get wet the straw underneath will still give a good hot burn to destroy the weed seed.” Pete has designed a narrow windrow chaff management system of his own that drops the straw on the ground and places the chaff on top to give a good hot burn to destroy the weed seed, even if the windrows get wet. Narrow windrow burning is done mostly in the wheat paddocks with a known brome grass history. In recent years Pete has achieved very good results using his modified narrow windrow burning system in paddocks with very high brome and ryegrass numbers. The main disadvantage of narrow windrow burning is that it removes all the crop residue. Chaff carts remove between 10 and 25 per cent of the crop residue but the rest is spread on the paddock and has a dual benefit of suppressing weeds and conserving moisture. Pete says the extra soil moisture can save a crop germination in a year with a dry start. Even so, nothing can replace narrow windrow burning completely in very high weed pressure situations so Pete will continue to use his modified narrow windrowing chute when necessary. Chaff carts have served a purpose but their time on the farm is limited and this harvest they will most likely introduce a chaff deck system to replace the chaff cart. Pete sees some advantages of the chaff deck system over chaff lining, such as less dust off the wheel tracks during spray applications and not having any piles of chaff impeding sowing. Pete reckons the iHSD will revolutionise harvest and weed seed control and thinks there could be opportunities for contractors to invest in iHSD machines to assist growers by harvesting their weediest paddocks. “Even under best operating conditions the chaff cart puts 50 per cent of the brome grass seed in the cart, 25 per cent on the ground and 25 per cent goes over the rotor and into the bin. The suction system of the iHSD reduces weed seed losses over the rotor making it a more efficient option,” he says. Pete follows a 5-year rotation of wheat, barley, lentil, wheat, lentil in large, 100–200 ha paddocks. He sows all crops on 25 cm (10″) row spacing at high seeding rate for increased crop competition and, where practical he sows paddocks east-west to gain better weed control.To improve soil fertility, chicken manure is applied at a rate of 3 t/ha every three years on paddocks that need it; often ahead of wheat. Deep ripping on the sand hills has been an effective measure to alleviate compaction and improve crop performance. Pete hopes to eventually implement a controlled traffic farming system that will help preserve the value of operations like deep ripping and also make the chaff deck system more effective. The Edwards are also lifting productivity and reducing weed pressure on their poorer sand hill soils by double sowing barley, wheat and lentil crops. In just a few years Pete has noticed a real difference in the soil structure and moisture holding capacity. Other resources: Implementing the WeedSmart Big 6 on the Yorke Peninsula

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