Preventing weed growth by enhancing soil systems | The Land

theland.com.au · Feb 19, 2026 · Collected from GDELT

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Myles Ballentine, a mixed cropping and livestock producer and owner of Brix Booster biofertiliser, was one of the guest speakers addressing topics of soil, carbon and water at the DCCA event held in Bauhinia. Picture by Bella Hanson.Most producers can tell you exactly how much rain fell last summer... far fewer can say how much of it stayed.Subscribe now for unlimited access to all our agricultural news across the nation or signup to continue readingAll articles from our website & appThe digital version of This Week's PaperOur entire networkThe event, facilitated by the Dawson Catchment Coordinating Association, pulled together producers, researchers and advisors to unpack what is quietly draining productivity across Brigalow grazing systems, often long before stock numbers or seasons come under scrutiny.Mick Alexander from Grazing Best Practices, Rockhampton, with a parthenium weed at Kurrajong Park, Bauhinia. Picture by Bella Hanson.Soil systems consultant Mick Alexander from Grazing Best Practices based near Rockhampton put it bluntly."We spend a lot of time fighting symptoms," he told the crowd. "But most of the time, the problem isn't the weed, it's the system the weed is responding to."When grass stops building carbon, weeds take the jobMr Alexander said the industry's default response to undesirable species (Indian couch, parthenium and other invasive grasses and broadleaf weeds) was often chemical or mechanical.But biologically, he said, those species are rarely the cause of decline.Mick Alexander said undesirable weed species are opportunists. Picture by Bella Hanson."They're opportunists," he said. "They move in when the soil stops functioning properly."At the core of his argument was carbon flow - the movement of energy from green leaf into the soil through roots.Every actively growing plant pulls carbon dioxide from the atmosphere and converts it into sugars. In pasture systems, between 20 and 50 per cent of that carbon is pumped below ground, feeding microbes that build soil structure, nutrient availability and water-holding capacity."When that process is interrupted by overgrazing, repeated second bites, or lack of recovery, you starve the soil biology," he said. "And once that happens, the system opens the door for species that are very good at surviving stress."Indian couch and parthenium, he said, are not signs of aggressive weeds winning, they are signs of soil under pressure."If you've got bare ground, compacted soil, low biological activity and poor infiltration, those plants are perfectly adapted to move in," Mr Alexander said. "Killing them without fixing the system just creates space for the next one."Why early grazing fuels weed pressureOne of the most quietly damaging practices discussed on the day was early grazing at the start of the growing season, often driven by the relief of seeing green after a dry spell. Picture by Bella Hanson.One of the most quietly damaging practices discussed on the day was early grazing at the start of the growing season, often driven by the relief of seeing green after a dry spell.Mr Alexander explained that when grass was grazed before it had rebuilt enough leaf area, it had no capacity to photosynthesise properly."So it mines carbon from its roots to regrow," he said. "That weakens the plant, shrinks the root system and reduces the carbon being fed into the soil."Over time, that pattern creates a paddock with shallow roots, poor structure and reduced microbial life - exactly the environment where Indian couch and parthenium thrive."Those weeds aren't breaking the system," he said. "They're exploiting one that's already broken."Water loss sets the trapMixed cropping, livestock producer and owner of Brix Booster biofertiliser, Myles Ballentine, from Banana tied weed pressure directly back to water movement."In a 600-millimetre rainfall zone, that's about 600 litres of water per square metre falling every year," he said."On average, only about 30pc is actually used by the system."The rest is lost through runoff, evaporation or soil that seals and sheds moisture, particularly where groundcover has been removed.Myles Ballentine said strategies to maximize water absorption in rain events in pastures will drastically benefit grass production over weed growth. Picture by Bella Hanson."When water doesn't infiltrate, grass doesn't compete," Mr Ballentine said."And weeds don't need much of an invitation."Side-by-side demonstrations showed how bare or compacted soil can begin shedding water within minutes of heavy rain, while covered soil continues absorbing long after rainfall stops.That difference, he said, is what determines whether a paddock grows pasture, or grows problems.The high cost of forcing a systemThe less productive pasture at Kurrajong Park near Bauhinia that had rows of leucaena planted, and was then ploughed in an attempt to increase pasture capacity. Picture by Bella Hanson.The Donoghue family learnt the hard way that in the Bauhinia district, sometimes the best management move is knowing when to walk away and let a paddock rest.Standing in a paddock at Kurrajong Park that had once been planted to leucaena long before they purchased the property, Annie Donoghue pointed out the frustration: despite being blessed with rich soils, the leucaena had struggled to mature. In late 2025, the family attempted to plough the area in rows, but they soon realised they were fighting a losing battle.Between mounting time constraints and the looming threat of poor results, they made the call to abandon the project and focus on other areas of the property to renovate. The less desirable pasture was a live demonstration of the theories shared by Mick Alexander and Myles Ballentine where the theories on Indian couch and Parthenium weed were evident.For attendees, it proved that heavy-handed intervention isn't a silver bullet for underlying land constraints."We realised how long it was going to take us," Ms Donoghue said. "So we abandoned it for this season and focused on country we could actually set up properly. "We were trying to force change before the system was ready, and that just created more stress for the pasture and for us."The takeaway for producers seeking increased pasture productionOne of the strongest messages from the day was that many weed battles are being fought after the real damage has already been done.Producers were urged to see Indian couch and parthenium not as failures, but as feedback."If you fix carbon flow, rest, groundcover and water infiltration, the weed problem often shrinks on its own," Mr Alexander said."And if it doesn't, at least you're treating the cause, not just the symptom."DailyDaily HeadlinesToday's top stories curated by our news team.