Simon Burgess, Conara Tasmania
Managing weeds through property development
Giving weed management a high priority during significant property developments at Vaucluse, on the South Esk River in Tasmania’s midlands, has paid dividends.
Proterra’s Vaucluse Agricultural Company purchased Vaucluse in 2015 and added neighbouring Glen Esk in 2016, taking the total area to 4400 ha. Between 2016 and 2022, the company undertook a major redevelopment of the mixed farming operation, focusing on new irrigation infrastructure.
Operating partner Simon Burgess says reconfiguring paddocks for pivot and hard hose travelling irrigators brought up many issues related to previous management and land use, not the least of which were weeds.
One pivot development on Glen Esk involved bringing seven paddocks – all with different soil types, history, fertility and weed burden – into a single management unit. There were also pine tree shelter belts, a silage and straw dump, fences, roads, pipelines and dams to contend with.
“We used EM mapping at the start of the development phase to identify drainage lines and soil suitability for cropping,” he says. “We then applied a robust knockdown herbicide to spray out the areas suitable for cropping and left the drainage lines and any waterlogged, rocky or bare areas unsprayed.”
“These areas tend to always be weedy, and it is best to leave them as non-production zones. Keeping waterways grassed to ensure good paddock drainage is very important here.”
After seven years of transitioning through the development phase and into the full production phase, the area under irrigation has almost doubled from just under 1400 ha to 2600 ha.
“Our weed management at Vaucluse acknowledges that if weeds are present, it is because that weed likes the ‘environment’ and farming practices,” says Simon. “So, we either change the current practices or accept the weed and move the affected area out of cropping.”
“Everything you do matters, whether it is the crop rotation, herbicide program, cultivation or burning because management practices often have lasting effects of 10 years or more,” he says. “To help avoid making poor decisions, we maintain open and frank communication with all on-farm staff and our external advisors.”
Simon and the agronomy team at Vaucluse have implemented a robust integrated weed management program that incorporates most of the WeedSmart Big 6 tactics.
Crop and pasture rotation
The Vaucluse aggregation is a highly integrated mixed farming operation with 11 different cropping and livestock enterprises on 2350 ha of arable land and 2050 ha of pasture. The cropping program usually includes about 1100 ha cereals (70% winter and 30% spring planted), 400 ha potatoes (some land is leased to other growers), 240 ha canola (110 ha fodder and remainder for grain), 230 ha poppies (often up to 500 ha), 120 ha legumes, 200 ha hemp and 60 ha carrot seed (leased out).
The property runs 200 Angus breeders and 4000 composite breed ewes and has a steady state of around 20,000 DSE, peaking at 70,000 DSE from April to July when there are additional sheep and dairy cattle on agistment. There is the capacity to increase numbers to 6000 ewes plus trading lambs.
Within the cropping program, the livestock has grazing access to 1200 ha of winter fodder crops and to pasture on non-arable land. Simon says that it is hard to get scalability in pulses, so winter fodder crops provide the main break crop benefits. The 1200 ha of winter fodder crops are planted in autumn, grazed over winter then sown to spring planted crops. A typical breakdown is 500 ha fodder wheat in paddocks with wild radish burden, 400 ha pasja (a leafy brassica) and 300 ha tillage radish to condition the soil and help control annual ryegrass.
Integration of fodder crops into the crop rotation helps to break weed and disease cycles and to transition from autumn to spring planting windows as required. Simon is not concerned about feed utilisation because everything ends up benefiting the soil biology. Each fodder paddock is matched with the most suitable class of livestock, and care is taken when choosing the site for feed pads in the paddock.
Simon uses Excel and Agworld software to forecast the crop rotation for the next four or five years. He bases crop selection on paddock history, weed burden and development stage. After harvest, the team reviews the next scheduled crop to ensure it is still the best fit. This discussion involves farm managers, consultant agronomists and machinery operators and includes any issues that arose in the season, such as disease pressure and weed escapes that might affect the following crop.
All crops are direct drilled where possible, but cultivation is used strategically in response to weed pressure and soil condition to incorporate stubble, manage weeds and even dry out the soil profile if necessary. Kelly Chains have proven beneficial in the stubble and weed management program at Vaucluse.
Herbicide planning and application
When bringing new land into the rotation, Simon starts with a robust chemical fallow and applies the required nutrients (including lime) based on soil testing. The team takes note of what plants come back after the chemical fallow and assesses the impact of the herbicides as an indication of potential herbicide resistance. They also conduct regular resistance testing on annual ryegrass and wild radish across the property.
Once the next crop is confirmed, Simon, the cropping manager and their consultant agronomist develop a plan for the crop to make sure they have the best combination of crop protection products to maintain efficacy.
There are 11 agronomists involved in managing their own crops, sharefarm crops and crops on leased land. Everyone is kept up to date with resistance status and emerging problem areas, and the herbicide program is adjusted as the season unfolds.
The onboard John Deere Operations Centre provides maps of all input applications and crop yield. Using the EM maps, Simon has started variable rate applications of lime, dolomite, phosphorus and potassium in their higher-value crops such as potatoes.
The inclement weather and short growing season in Tasmania’s midlands make the timing of operations particularly critical. Simon does not hesitate to bring in contractors if a particular job can’t be done in time with their own staff and machinery.
“Timing of weed management operations must suit the environmental and plant conditions,” says Simon. “For example, we never apply clethodim just before or just after a frost event.”
Spray operators at Vaucluse are highly trained and are actively involved in planning and implementing the herbicide program. They are also involved in the design and implementation of on-farm trials, and regularly attend field days.
Simon does not usually implement a glyphosate–paraquat double-knock to protect glyphosate. He has found that a double-knock of glyphosate before planting spring barley successfully disrupts annual ryegrass populations at Vaucluse.
“Spring is a good time to hit ryegrass while it is actively growing, and spring barley is one of the few crops that can really put pressure on ryegrass seed production,” he says. “Varying the time of sowing crops is very beneficial when managing ryegrass, and strong crop competition is a good way to drive down the weed seed bank and minimise the risk of glyphosate resistance.”
Fodder cropping is central to the weed control program at Vaucluse. Simon selects strong, fast-growing and disease-resistant fodder crops to maximise crop competition. Each crop is chosen to combat the main weed in the paddock, for example, spring-planted barley and hemp are used to combat annual ryegrass issues.
Although autumn planting is common practice for cereal crops in Tasmania’s midlands, Simon has introduced more spring cereal planting to their rotation to provide more competition to weeds.
Slower crop establishment and early growth can give weeds an opportunity to establish in autumn, so they often delay planting their autumn program to avoid frost risk and use the opportunity to apply pre-seeding knockdowns.
All crops are sown on narrow row spacing 25 cm (10 inch) and at high seeding rates to maximise crop competitiveness.
Stop seed set
All headlands in cereal crops are cut for silage or whole-crop hay to stop weed seed set. This provides a source of fodder for their livestock and agisted stock while limiting the encroachment of weeds from fencelines and other non-crop zones.
“If there are particularly weedy patches, we terminate the crop in these areas early,” says Simon. “Some areas have had ryegrass infestations so bad that we cut the affected areas for silage and sprayed the re-growth. Another time the grass weeds in a green manure crop were bad, so we switched to a chemical fallow over winter with four knockdowns applied from April to October.”
Within the Vaucluse aggregation, there is 8 km of council roads, 7 km of highway frontage and 5 km of river frontage. To minimise the movement of weeds, the team manages external infrastructure themselves wherever possible.
Harvest weed seed control
By harvest, most of the annual ryegrass plants have shed their seed, so harvest weed seed control tactics are of less value in the Tasmanian midlands than in other regions.
In weedy paddocks, Simon will often windrow crops and bale or burn the stubble to destroy or remove as much weed seed as possible.
Note on property ownership: Proterra’s Vaucluse Agricultural Company sold in Nov 2022. From 1 March 2023 Simon Burgess is no longer associated with the management of the Vaucluse aggregation.