Badgingarra grain grower, Colin McAlpine, avoids dry seeding like the plague and reckons that has been the key to his success with regaining control of herbicide-resistant weeds on the 4000 ha of cropping land he owns and leases.
Starting with a mainly-livestock enterprise with a high weed burden Colin has greatly reduced the weed numbers in his mainly-cropping enterprise in less than ten years, taking advantage of the fact that herbicide resistance levels were still quite low. He has used a variety of tactics to protect the herbicide modes of action available while hammering down the weed seed bank every year.
Twelve years ago Colin moved from the eastern wheatbelt to the Badgingarra district in the central-west wheatbelt where the incidence of frost is lower and the annual rainfall higher, averaging 550 mm. He soon found that the higher rainfall and non-wetting soils presented significant management challenges in the form of staggered germination of weeds.
Colin does no dry sowing, and believes that the practice puts too much pressure on pre-emergent herbicides, often leading to a blow-out in herbicide-resistant weeds.
“It takes real determination to leave the seeder parked in the shed when other growers in the area are out seeding their paddocks,” he says. “Instead, we wait for rain and the subsequent germination of weeds. We do a double knock of glyphosate followed with either Spray.Seed or paraquat, always at full rates. The aim is to germinate and kill as many weeds as possible before we seed.”
“I never use glyphosate on its own and always follow through with the double knock,” he says. “In just eight years we brought resistant populations of radish, brome and silver grass under control on our home farm.”
Resisting the urge to start planting earlier takes a high level of confidence in the value of the double knock to clean the paddocks up before sowing, reducing the number of weeds that the pre-emergent herbicides need to control at seeding.
“We have seen the results and although the crops may sometimes seem a bit behind other crops in the district we have much less in-crop weed pressure,” he says. “The profitability of our crops is higher because we have consistently solid yields and our costs of production are no greater than average.”
Annual ryegrass and wild radish have been the main problem weeds on his farms and Colin has taken on the challenge of running down the weed seed bank without allowing herbicide resistance to evolve.
“We have thrown everything we have at weeds and have been testing weed seed for resistance every year so that we are always ahead of the game,” he says. “We only have a small number of herbicide modes of action available so we can’t afford to lose any of them.”
Colin has thrown everything he can at reducing the weed burden on his farm while taking all precautions to protect the available herbicide modes of action.
Colin grows noodle and prime hard wheats and malt barley, as well as canola and lupins. He chooses sowing rates at the upper end of the range to achieve strong crop competition and finds barley is the best competitor against weeds.
To further favour the crop over weeds, Colin has moved from 30–33 cm (12–13 inch) row spacing to 25 cm (10 inches) on one seeder and the second seeder is set to sow paired rows at 23 cm (9 inch) spacing.
Colin has used narrow windrow burning in some years but has also had success using a ‘cold burning’ technique. “We cut the crop short and spread the residue, then after it rains we burn off the residue and find that we destroy a large portion of the weed seed present,” he says. “Having less crop residue allows better soil contact for the pre-emergent herbicides, improving their efficacy, and the weed seed numbers are less of a challenge.”
Colin’s overall weed management program has been so successful that he has not needed to do any burning in the last two years.
Sheep also feature in the weed management program with 2500 breeding ewes and their prime lambs graze on crop stubble over summer. “The adult sheep remove any weeds growing after harvest and also stir up the soil, helping to stimulate new germinations of weeds,” he says. “They also breakdown the stubble and improve the water penetration into these non-wetting soils.”
Colin manages the farms in 600–800 ha blocks and once he has used a mode of action in the block he does not use it again in that block for three years.
In the 800 ha canola block each year Colin uses as many weed control strategies as possible to clean the block up ready for the cereal phase. At harvest Colin sprays glyphosate under the swathe and puts the ewes in straight after harvest. Roundup Ready canola is used just one in every four canola seasons to avoid the risk of glyphosate resistance.
In recent years Colin has reduced the row spacing from 30–33 cm (12–13 inch) to 25 cm (10 inches) on one seeder and the second seeder is set to sow paired rows at 23 cm (9 inch) spacing to increase crop competition while maintaining strong yields.
On the sandier soils Colin grows lupins as the break crop, using crop topping as another tool to target late germinations of weeds and any survivors. He times the crop topping spray to suit the maturity of the weeds present and accepts any yield loss that might cause.
“Short-term economics does not always support weed control strategies,” he says. “I believe we have to play the long game and do things now that will limit the cost of weed control in the future.”
Colin believes there are distinct advantages in owning and operating your own spray equipment to make sure herbicide is always applied at the best time.
“Getting good advice from an agronomist is also very beneficial,” he says. “Some herbicides have very specific requirements to meet when it comes to timing or optimal conditions. Having a technical advisor helps make the most of every application.”
He has invested heavily in liming to raise the soil pH and in improving the soil nutrition and biological activity across the clay loam and sandy soil types. “Every four years we apply lime to keep the pH around 5.8 to 6.2,” he says. “This improves plant growth and also makes the pre-emergent herbicides more effective.”
Completing a double knock within 10 days of rain and before seeding means Colin needs to cover a lot of ground very quickly with the sprayer. Using a nurse tank in the field he is able to cover an additional 30–50% larger area than if he had to fold up the sprayer and return to the shed each time the sprayer needed refilling. Using modern spray equipment he is also confident that he is applying the right droplet size at the right pressure for the particular herbicide. “High water rates are critical to achieve good results,” he says. “The aim is always to be treating actively growing weeds when the soil is moist. Dusty conditions are not good and it helps to have some crop residue on top of the soil.”
Colin usually has 1800 to 2000 ha of wheat, 800 ha barley, 800 ha canola and 500 to 600 ha lupins in each year. He finds the longer rotation helps preserve herbicides and avoids using the same herbicide two years in a row.
“When we came here the property had only a small area of cropping and the weed numbers were very high from the predominantly grazing use,” he says. “In our early years our wheat crops were yielding around 2.5 t/ha as they struggled under poor soil health and high weed conditions. Since then yields have steadily increased to average 4–5 t/ha and I can confidently market the wheat knowing that we can achieve the yields required.”