Mouldboard ploughing + Chaff lining + Grazing
Andrew and Gina Kenny farm at Badgingarra, in WA’s west midlands using an integrated program of crop rotation, mouldboard ploughing, grazing and chaff lining to keep their weed numbers very low.
Andrew’s parents, Mike and Sara, arrived in the Badgingarra district to farm in 1959 and started clearing the land for cropping, at about the same time cropping land was also being developed around Esperance.
“There is a fault line that runs through the property with distinct soil types on either side,” says Andrew. “On one side of the line is our best cropping soil – clay through to pea gravel; on the other side is white sand with very limited water holding capacity, which we use mainly for grazing.”
Grazing to maximise productivity
About 60 per cent of the 4150 ha property is used for continuous cropping and the rest for grazing sheep. The Kennys grow some hay for their own use and the sheep also graze the crops – mainly barley, and sometimes wheat and canola – from mid-June to mid-August.
For over ten years the Kennys have run 5500 ewes in two flocks – a 4000-ewe self-replacing merino flock and 1500 Prime SAMM ewes mated to Poll Dorset terminal sires. Producing both wool and meat, the sheep are an important component in the business. SAMM are a dual-purpose sheep that was later further developed to produce a heavy slaughter lamb at a young age, as well as good quality wool.
“We grow mainly Bass and Planet barley, which we will graze two or three times with 2500 hoggets before allowing it to finish for grain,” he says. “These varieties both tiller well and respond quickly after grazing to the first node stage.”
Low weed numbers allows dry sowing
Once the season breaks, the Badgingarra area can generally rely on good rainfall through the growing season. In 2018 there was a late break, resulting in Andrew taking a risk and sowing 75 per cent of their crop dry. That year he saw the benefits of earlier sowing and is confident that their weed numbers are now low enough to make dry sowing a safe practice.
“On the heavier soils we grow canola, wheat and barley. Sandier soils that are lower in the landscape have better nutrient levels than those at the top of the landscape, and are suitable for cropping lupin, wheat and barley.”
Barley has been a consistently strong performer in recent years so the area has increased. Lupins provide a good break from cereals and provide a high protein feed that is easy to store on farm and kept primarily as a drought reserve.
The Kennys introduced canola to their cropping program in the 1990s and have used TT canola, swathing and spraying under the swather with glyphosate as key tools in their weed control program. They also crop top Barlock lupins to stop seed set.
Andrew rotates herbicide modes of action through the crop cycle, particularly with the pre-emergent chemistry – using propyzamide in lupin, trifluralin in canola, Sakura in wheat and trifluralin + metribuzin in barley. He also targets weeds ahead of seeding with a double knock of glyphosate then paraquat, or uses Spray.Seed®(paraquat/diquat) on its own.
In weedy paddocks Andrew avoids growing two barley crops in a row, choosing instead to switch to canola or lupins to utilise other herbicide MOA, but in paddocks with very low weed numbers he will occasionally grow barley on barley to boost profitability.
With few in-crop options for ryegrass control, Andrew relies on having clean paddocks at seeding and robust pre-emergents. To ensure the crops get off to a good start, Andrew buys in hybrid canola seed and uses a mobile contract seed cleaner to clean farm-retained cereal and lupin seed. He has increased crop competition using a paired row boot on a 30 cm spaced tyne bar to give an effective row spacing of 7.5 cm.
“The tynes are custom built and we use them for sowing all our crops,” he says. “They probably work best in the cereals, but we don’t have any problems in the other crops either. The aim is to do everything we can to increase crop germination, which gives us more crop and less weeds for the same amount of effort.”
Burying glyphosate resistance
Andrew says annual ryegrass and wild radish continue to be their most challenging weeds and he has recently added RR Truflex canola hybrid to the rotation to give more options to use glyphosate.
“I am very conscious of the risk of accelerating glyphosate resistance and so we also use mouldboard ploughing to bury glyphosate resistant weed seeds and improve the wettability of the sandy soils,” he says. “Mouldboard ploughing has fixed non-wetting issues wherever we have used it and this improves crop germination, but on the very sandy soil fixing the non-wetting is not enough to sustain cropping, so these poorer soils remain under pasture.”
The benefits of mouldboard ploughing for weed control varies according to soil type. Andrew has seen it most effective on their sandy soils but found it difficult to achieve full inversion on the gravel country.
Chaff lining suits sheep
Ten years ago Andrew began narrow windrow burning for harvest weed seed control, mainly in cereals and only in weedy paddocks. They had good results in weedy paddocks but after eight years Andrew was looking for an alternative that would have less impact on nutrients and require less labour.
“We graze the stubbles over summer and the sheep would make tracks through the narrow windrows, which increased the number of places the windrows needed to be lit,” he says. “In 2017 we decided to give chaff lining a go.”
Although the farm is not set up for controlled traffic, Andrew does run the harvester on the same lines each year, allowing him to place the weed seed in the same place each season. With the chaff lining chute as a semi-permanent modification to the harvester, Andrew is now able to implement HWSC in all crops and all paddocks.
“The chute, baffle and spreader chopper were fabricated and fitted for around $6000,” he says.
In addition to concentrating the weed seed, chaff lining also concentrates any crop seed losses out the back of the harvester. This means the sheep can make use of any lost grain and Andrew expects the productivity gains from chaff lining would be similar to that measured for chaff dumps.
“In 2018 we had a high level of weed germination in the chaff lines but we did not treat them differently to the rest of the paddock,” says Andrew. “The chaff chute left clumps in the paddock and I thought this might lead to seeding blockages, but in reality, the tyne seeder easily worked through the fine chaff material.”
Andrew expects there would be some rotting of the chaff and weed seeds in years with wetter summers, but this has not yet been put to the test. What is evident though is the impact of higher soil moisture retention under the chaff lines.
Sheep graze the stubbles and do a good job of stopping seed set on any green ryegrass that escaped capture at harvest. The sheep also reduce the overall stubble load and trample the chaff lines, making sowing easier.