Snapshot

• Grower: Jake Hamilton, his wife Felicity, father Scott and his wife Janne
• Property: Krui Pastoral Co, Condamine
• Farm size: 5600 hectares
• Average annual rainfall: 573 millimetres
• Soil types: grey/brown vertosols, red kandosols, highly sandy creek country
• Cropping program: wheat, barley, chickpeas, faba beans, sorghum, mungbeans and, very rarely, dryland cotton.

At the end of 2020’s harvest, 30 millimetres of rain fell at the Hamiltons’ Condamine, Queensland, property. A decade or so ago this would have seen a plethora of weeds emerge. Last year, the only weed that germinated was fleabane, along with some crop regrowth.

It has been more than a decade since the Hamiltons began the process of using integrated weed management (IWM) practices on farm and the benefits are seen each season.

Jake and Felicity Hamilton, and Jake’s father Scott and his wife Janne, farm 5600 hectares on the western Darling Downs, where the visual reminders of their weed success are satisfying. “We have got the seedbank to a very low level, making it easier to control and it is now paying off,” Jake says.

The trigger to move to IWM was glyphosate resistance. “When resistance was identified in the mid-2000s we made a decision to move to a more robust IWM program. Our main aim became to stop weed seed-set at all costs.”

Process

One of the first steps was to move to more efficient technology, Jake says. Faster, more mobile, self-propelled sprayers were bought. “It used to take at least 30 minutes to fold up the old Flexi-Coil tow behind the sprayer to change paddocks.”

Now the sprayers take less than a minute to get going. “We don’t even get out of the cab, making the process much more efficient. On level ground we can travel at higher and more consistent ground speeds to cover larger areas quicker.”

Timely herbicide applications mean the farm can be sprayed in just seven days. Other IWM practices used include high seeding rates to create strong crop competition, an in-crop and summer residual chemistry program, and some optical spot-spraying. “Together they have reduced our weed seedbank to very low levels.”

Additionally, sparse, hard-to-control weeds such as feathertop Rhodes grass are managed by spot spraying using a mobile spraying unit on a John Deere Gator.

Water management

The Hamiltons’ IWM journey is part of a broader program to improve on-farm water use and soil fertility. Reducing weed pressure helps ensure moisture is kept for crops – but it is the wet years that can be more problematic.

This is because melon holes, characteristic of brigalow soils, dot the landscape on 3000ha of the farm. “Wet years, rather than dry, are bigger problems when you have melon holes. Extreme waterlogging can occur from a single rainfall event. This also leads to nutrient and organic carbon leaching laterally and accumulating at the bottoms of the holes. This leaves the tops bleached, infertile and unable to hold moisture.”

With summer crops not always an option because of the heat and unreliable rainfall, Jake has used this time to continue the levelling program. This addresses not only melon holes, but gully erosion on some steeper country and contour bank construction to prevent future damage.

Melon holes are naturally occurring depressions, surrounded by associated mounds. “You can be watching a header out in the field and it will completely disappear from sight down a melon hole. They can be up to four metres deep. It’s like having a field of small hills. On country with some of the worst melon holes, we are moving 550 cubic metres of soil per hectare, although the average is 300 cubic metres.”

This summer the plan has been to level 300ha of melon holes.

Jake’s father Scott started levelling in 2006 with local grower Ben Taylor. “Back then, we levelled 40ha of our worst melon holes with his GPS bucket so we could measure improvements and see what constraints we had. We considered the trial a success. The block has out-yielded its surrounds every year since, regardless of the season.”

However, it was the 2011-12 floods that cemented the need to do more, Jake says. “We lost a lot of country to waterlogging that season, which made planting the 2012 winter crop an absolute nightmare. Even by May, up to 30 per cent of the surface was under water in some fields.”

Over the years Jake has used a combination of precision agriculture tools, such as comprehensive calibrated yield maps, satellite NDVI (normalised difference vegetation index) and high-resolution aerial imagery, to better understand where waterlogging has caused yield and constraint issues.

“Yield maps and NDVI imaging have helped to identify low biomass/yield areas that require investigation and we generally map soil constraints and waterlogging. We then use these maps to create variable-rate prescriptions for applying ameliorants.”

More recently he has used an aerial, high-accuracy LiDAR elevation survey to plan the levelling work and contour bank construction.

Aerial surveys can be cost-prohibitive, but with other neighbours it became achievable. “MCA Agronomy organised it for their clients. Despite not being a client, I was lucky enough to be included. It cost about $3/ha and the data is helpful to all of us.”

LiDAR – or light detection and ranging – is a remote-sensing method used for measuring the exact distance of an object on the earth’s surface. Jake says that data proved critical in designing the levels, which took months of late nights, painstaking maths, and trial and error.

The contour banks are unique because they follow a graduated design, which means the banks get larger in size as the length and water volume increases. “This achieves a 60 per cent efficiency gain because we are reducing the amount of dirt that needs to be shifted. It follows a formula we developed and was made possible by the land forming design software from T3RRA.”

The banks will help prevent future damage from gully erosion on steeper country where water can run across the surface, taking topsoil with it.

Although the farm is not in the reef catchment and therefore not subject to those regulations, it is something the family is keen to be abreast of. “We don’t want to lose that soil and see it run into waterways. Levelling solves waterlogging issues by controlling water flow across the soil surface and allows us to begin to repair uneven soil fertility.”

Jake and Felicity Hamilton farm 5600 hectares at Condamine, on Queensland’s western Darling Downs. Photo: Jake Hamilton

Benefits

Despite the effort involved, the benefits are worthwhile. Jake says spraying efficiency and application evenness improves immediately. “Higher, more-consistent ground speeds can be achieved and machine damage due to ground strikes is eliminated.”

Harvester performance also improves. “It allows for more-consistent and level machine operation. It is not rolling around side to side and up and down. The same could be said for seeding accuracy and tractor efficiency.”

As an example of the benefits, Jake says that 2019 was a reasonable year crop-wise despite no in-crop rain. “Our plan in regard to fallow and stubble management, crop rotation and fertiliser, meant that in 2019 we were able to grow a reasonable crop on nil growing season rainfall. So, for us, we would consider too much water, rather than not enough, to be a bigger issue. All we can do is try and mitigate the damaging effects of heavy storms and extremely wet seasons, and our earthworks and levelling plan is part of that.” 2020 was also better than the average season, despite a dry finish.

Levelling lessons

For other growers considering major levelling and earthworks, Jake has some suggestions. “Don’t be afraid to spend the money when it’s dry, you’ll appreciate it when it turns wet.”

It is important to ensure an accurate survey is done, he says. “Spending a bit more on a higher-quality survey in the beginning will lead to greater savings down the track as levelling efficiency can be increased. You’ll end up shifting fewer cubic metres per hectare to achieve the same result.”

In the same manner, he says, a good field design is extremely important. “A good machine following a bad design will get undesirable results. Also, soil test before levelling so you are aware of any subsoil constraints that may be exposed so they can be considered in the design.” During his earthworks, Jake started a deep fertiliser application program.

When the large earthmoving machinery moves on and leaves more-level paddocks and new contour banks, the Hamiltons will get busy with their winter cropping program. Faba beans and barley are planted in April, followed by wheat and chickpeas in May.

The winter cropping program is more important than summer for the Hamiltons. “Summers are hot, dry and unreliable. Sorghum has only been successful twice in the past decade (in 2013 and 2018).”

Scott believes it might even be a crop of the past for the farm. “The summer heat means we may not grow it successfully much more.”

More information: Jake Hamilton, 0427 228 194, jake@kruipastoral.com, @HAC_Qld