THE RIGHT STUFF: Farmer Mark Modra has his eyes on many methods to combat problematic weeds in the pursuit of greater productivity.

THE RIGHT STUFF: Farmer Mark Modra has his eyes on many methods to combat problematic weeds in the pursuit of greater productivity.

Looking for tech killer, not filler

Weeds feel the full force

The Knowledge Bank

Success with non-chemical weed reduction measures


This article is sponsored by Rabobank

EYRE Peninsula farm Mark Modra says weed control is the most critical part of his enterprise.

“Keeping on top of problem weeds such as ryegrass and wild radish is the biggest obstacle to profitability,” he said.

To this end, he is prepared to look at a range of control methods, from some of mankind’s oldest methods of keeping weed burdens down to cutting edge technology, including robotics.

But Mr Modra is hard-nosed about the economics of technology and while constantly on the look-out for new solutions he says they have to be able to demonstrate an economic return.

“I don’t want tech for tech’s sake, just to have a cool new toy,” he said.

“There’s a lot of stuff I look at and I think that is fantastic how they have developed that but I can’t see how it will pay in terms of the enterprise here,” Mr Modra said.

He said he saw the major applications for technology in his business in weed management and also in terms of handling nutrition inputs.


At present, Mr Modra is having good success with a decidedly low-tech solution.

“The use of a chaff cart to collect weed seeds has seemed to work really well, we’ve put out the heaps and allowed livestock to get in on them, not only does it lower the amount of weed seeds the availability of feed means we can run high stock ratios too,” Mr Modra said.

In the past he has burnt the chaff piles, but now he grazes them and has eliminated the burning.

Not only have the livestock put an end to burning, Mr Modra said the nutritional value of the chaff heaps had been a boost to sheep growth rates.

“We’ve increased stocking rates 50pc over summer solely due to the chaff heaps.”

“I think having non-chemical measures to combat weeds is critical, in particular when you see the rates of resistance to key chemicals,” he said.

He said while the system was not flawless in terms of eliminating weed seeds it was better than 90 per cent effective.

“I know 5pc of ryegrass seeds go through sheep and that figure rises to 8pc for wild radish, but I’m pretty happy with that.”

The chaff carts need to be emptied anything between one and three boxfuls of grain.

“It can be a bit slow, especially when you want to push on at harvest time, but the key for the long term is getting that weed seed bank down.”

Although presently Mr Modra is working with one of humanity’s oldest weed control methods in grazing, he also has an eye to the future.

“I think there is definite merit to the concept of robotics and automation in terms of creating more non-herbicide options for weed control.”

Mr Modra shows this year's canola crop germinations.

Mr Modra shows this year's canola crop germinations.

“Using smaller, automated machines and green seeker technology between the rows you could have a machine with a tine chip the individual weeds out.

“Steam or sticky foam are both being used as well in similar systems where jets are opened when the machine spots a weed and I think this could also be a viable option.”

Mr Modra said the problem with these types of weed control systems was the speed of operation.

“The problem is you’re not going to be going along at 10kph, it will need to be done slowly which is why I see automation as important as you don’t want to tie up a lot of man hours operating the machine.”

Mr Modra said he would be keeping an eye out on tech advances, but said at present he was content to wait before investing.

“The problem with early adaptation of some farm technology is that it can cost more for the technology than the net benefit.”


He has an eye on what can be achieved in weed management with non-chemical means because of ongoing issues with herbicide resistance.

“We have lost our group A and B herbicides, the clethodim and sulfynurea products and there are concerns surrounding Clearfield herbicides, so we need to have other options.”

Worrying, Mr Modra said there were even early signs of resistance to Australia’s most widely used broad spectrum herbicide in glyphosate.


The Modra family farm over a number of properties on the lower Eyre Peninsula with diverse rainfall and soil types, from Yeelanna / Cummins in the centre of the EP  to coastal regions.

“We have places inland and closer to the coast, the soil type can vary from sand over buckshot gravel to nice red loams.

“The rainfall is also variable, from 400 to 500mm, the further south the higher the rainfall.”

An abundant mix of barley clover.

An abundant mix of barley clover.

He said the basic rotation was canola – cereal, either wheat or barley – legume, usually lupins.

“At Cummins the soil means we can grow lentils and beans, but the southern country is too acidic.”

He said he hoped faba beans, more tolerant of acidic soils, could be pushed further south with a good liming program and advances in inoculant technology.”

“Liming is important, but the new inoculants are a real cause for optimism, they seem to be getting good results in terms of nodulation on the southern block.”

The various soil types have different strengths and weakness.

“The stuff closer to the coast is beautiful in terms of draining, but it only has a holding capacity of around 20mm.”

“However, you generally don’t need as much stored moisture as there are frequent coastal showers, which seem to really suit canola, while inland is better for the pulses.”

In terms of machinery, Mr Modra said most of his gear was not particularly new.

Mark Modra and one of his employees, Alex Chevallier, alongside one of the farms fertiliser spreaders. The farm is over several properties on the lower Eyre Peninsula.

Mark Modra and one of his employees, Alex Chevallier, alongside one of the farms fertiliser spreaders. The farm is over several properties on the lower Eyre Peninsula.

If he buys new equipment he tends to prioritise harvesters and boom sprays over tractors.

“The technology evolves quicker in that space,” he said.

There are two seeders, a tined Flexi Coil machine and a disc.

“I do like aspects of the disc seeder, it is good in terms of handling stubble and inter-row sowing and you have zero soil disturbance but there are minuses, you can’t use a herbicide that requires incorporation such as trifluralin.”

The tined machine is set on nine inch (22.8cm) spacings, while the disc is on 15s (38.1cm).

In general he said the sowing program was done roughly half and half, according to the season and sowing logistics.

The disc seeder generally stays on the northern properties due to its ability to get through the higher biomass of crops there, while the tined rig normally remains in the south.

Mr Modra said he was happy to grow most of his canola closer to the coast.

A healthy crop of flowering canola.

A healthy crop of flowering canola.

“The rough rule of thumb is that canola should yield half of your cereal crop, on the coast we average 3-4 tonnes a hectare of cereal and we can reliably grow 2-2.5t/ha of canola, so it outperforms the cereals in that environment.”

“The climate suits, you get cooler, moister conditions which keep the crop in flower longer and you are less exposed to the risk of heat shock.”

“The issues are ensuring the crop has enough sulphur (S) and the leaching of nutrition, you need to keep a lot of nitrogen (N) up to the plants.”

The N is applied in granular form, while sulphate of ammonia provides the crop with S.

“We tried liquid fertiliser and it didn’t seem to give any noticeable difference.”

In terms of cutting nutrition costs, Mr Modra said he was looking at variable rate applications of fertiliser and soil ameliorants, combining yield maps and normalized difference vegetation index (NDVI) imagery.

“You could use the NDVI to identify patches of high and low biomass, ground truth it with the yield mapping and treat the different zones accordingly.”

Mr Modra said keeping the weed seed bank down is the key to good returns.

Mr Modra said keeping the weed seed bank down is the key to good returns.

Come harvest time the crops are often crop-topped with a desiccant.

“We find it is a good way of managing those late germinations of problem weeds.”

“The late germinations are often the reason you struggle to get on top of the weed seed bank, so we see a pre-harvest crop-topping as a good strategy where possible.”


In terms of ways to grow the business Mr Modra said while land acquisition was an option, he felt soil renovation on poorer quality soil types was another means to boosting productivity.

He said he has been working on clay delving on the sandier soils for some time.

“There is a clay level at around 500-600mm below the surface and we are working at delving and spading this clay to improve soil structure.

“You see a great response a lot of the time in the first year, but it is not predictable in terms of where you get the boost.”

He said the soil renovation generally cost between $400-500/ha, more if a soil amelioration program was included.

“We put on six tonnes of lime a hectare in some places to combat the acidity.”

While there was a significant cost, yield boosts can also be substantial.

“There was 0.6t/ha increase in wheat yields, the issue will be how long do the benefits last.”

“I’m often finding you get a boost for two years then it tapers off, but it is completely unpredictable, sometimes the benefits can last much longer, sometimes you only get one year.”

The key is to maximise the amount of seasons that see the yield boost. - Mr Mark Modra

“We really want to have the extra yield for 15 years rather than two years – but we’re yet to really figure out just why and where the delving works effectively for longer periods of time.”

In terms of soil health, Mr Modra is again looking at robotics.

“I like things like the Swarm concept being used in Queensland, a lot of small machines out in the paddock, it is not compromising soil health through compaction like you are with bigger gear.”

“Down the track it may allow us to do away with controlled traffic, which has big and heavy machines and can be difficult to implement.”

At present Mr Modra operates a semi-controlled traffic system, with most equipment on two metre centres.

“The spray unit is a modified truck fitted with large tractor tyres, but it cannot go out to three metres which is the main reason I have the two metre system.”

“Sometimes I would like to go out to three, but then you have things like moving equipment on the road at night, so there are logistics to consider as well.”

He said spraying, spreading, sowing and harvest were on the same 2m width.


The Modras were among the first families in the district to go continuous cropping, much to the scepticism of neighbours.

“Neighbours said with these soils you would run into nutrient deficiency – we found we could manage that OK, but weed resistance has proved a different story.”

With this in mind Mr Modra has brought livestock back into the enterprise mix.

“It is another tool in the toolbox, you can manage weedy paddocks with a pasture phase.”

“We switched a lot of the ground dedicated to lupins in continuous cropping to a legume pasture.”

“It is also a good way to utilize poorer soils, the returns in these areas from livestock are probably better and more consistent.”

The livestock enterprise is simple – young ewes are bought in and lambed down to a prime lamb sire.

Lambs are then sold according to seasonal prospects.

“Simplicity is definitely the key to the livestock business, but it is something we are getting great value out of, especially with wool and sheep meat prices where they are.”

Mr Modra said work on the farm was split up between himself and employees Alex Chileier and Robbie Siviour.

This article is sponsored by Rabobank