Waging war on weeds: the latest research

laser weed control
Blasting a weed with a laser, leaving it smoking with a high voltage zap or watching it wither under a giant magnifying glass may well be my cathartic farm job of the future.

Waging war on weeds – whether with chemicals or tillage – is set to get a whole lot smarter, more cost-effective and kinder for the environment, thanks to new work at the University of Sydney.

I was delighted when researcher Michael Walsh agreed to give Milk Maid Marian a sneak peek at the direction of his team’s research.

MMM: Farmers traditionally use chemicals or tillage to control weeds. Why should we consider new forms of weed control?

MW: Like many other decisions on farm, cost is the driving factor behind the need to consider other forms of weed control. Herbicides and tillage are both relatively cheap to apply but there are production risks to the use of these treatments.

There is a risk of herbicide resistance that occurs every time a herbicide is applied and once resistance evolves it remains in a weed population forever and therefore the herbicide is no longer useful.

For tillage it is the risk associated with soil disturbance and the lack of selectivity. In a pasture tillage for weed control will result in the loss of grazing for that paddock.

MMM: What are the alternatives being researched at the University of Sydney?
MW: We have been evaluating targeted tillage and more recently laser weeding, but we are also keen to investigate electrical weeding and solar weeding.

Electrical weeding is simply just using electricity to “shock” weeds. A weed is touched with a positive terminal and the earth acts as the ground so the charge passes through the weed burning cells as it goes. In the UK there are commercially available hand held electrical weeders.

Solar weed control

Solar weeding is using the sun to burn weeds. It’s the magnifying glass approach where a lens (grooved plastic sheet) is used to concentrate sunlight on to a weed to burn it. These types of lenses (Fresnel lens) are used in lighthouses to focus light into a strong beam.

MMM: What are the benefits?
MW: Initially the main benefit will be the reduced reliance on herbicides.

There will be substantial savings in weed control costs associated with controlling individual weeds rather than applying a blanket weed control treatment to the whole field. These savings will depend on weed density and it is hope that with good weed identification systems we will be better able to reduce weeds to very low numbers in crop and pasture paddocks.

MMM: Other forms of automated weed control have struggled to identify weeds in pasture. How can this be overcome?
MW: The development of new camera and sensing technologies for cars and phones has created the opportunity for weed recognition and identification. This will allow us to use tillage and other physical weed control tactics to selectively target weeds in crop and pasture situations.

MMM: What needs to happen to make this technology a reality on Australian dairy farms?
MW: I guess the first thing to do is to start working on systems that are able to identify weeds in pastures. Basically it is just a matter of training a sensing system (e.g. a robot) to recognise what is a weed and what is pasture plant. This is typically achieved by building up a library of weed images as they occur in pastures over the growing season.

Thank you very much, Michael, for this glimpse of what farmers can look forward to in the war on weeds! I do hope the dairy community is quick to support such an exciting development for farmers and the planet and can begin building that library of weeds.

Intensified farming good for the environment sometimes

There is so much to learn on a farm. Aged just 5, Zoe can correctly identify plants from rye grass to melaleuca, wildlife from willy wagtails to wedgetail eagles and stock from heifers to old cows.

Yesterday, she came across the beautiful Paterson’s Curse for the first time. It’s not a problem here – the occasional plant pops up from time to time. Zoe took this pic to remind herself of it.

Patersons Curse

Patersons Curse

When I was Zoe’s age, ragwort was the weed we battled all summer. The paddocks turned a buttery yellow in late spring and the grass and other weeds on the river flat scratched at the ute windows. I haven’t seen a ragwort plant here in years and though the blackberries and thistles persist, they are at vastly reduced levels. The grass is also tamed to juicy, shin-high herbage. I think it comes down to the intensification of dairy farming in the last 30 years.

When my brother and I were out in the paddocks pulling up ragwort in the late 1970s and early 1980s, we had 120 cows on 300 acres. Now, we milk 265 cows on about the same area (with dry stock on another 200 acres), although we might be a bit overstocked. Back then, we had three paddocks and now we have 24 on the milking pastures.

Someone reminded me that Dad never paid any attention to daylight savings in the 1980s because he couldn’t find the cows in the dark in those massive hundred-acre paddocks! Now, they are contained in 3 to 4-hectare paddocks. It means the grass is far better managed and forms a thick sward that is harder for opportunistic weeds to penetrate. It also means we are more alert to changes in the pasture – there are no more “lost forests”.

Weeds are part of my master plan

Zoe with marshmallow

Marshmallow is just one of the weeds to take off this season

“Weeds are part of my master plan” sounds like a phrase the Dr Evil of Dairy might use, doesn’t it?!

We’ve had a brilliant summer and autumn, which has made the grass and, ahem, the weeds, grow like crazy. Of course, there’s always a silver lining to every cloud and we’re seeing this as an opportunity to eradicate large banks of seed that has acccumulated over time without germinating.

Naturally, the weeds grow best on our best land, the river flats. The flats are next on my list of priorities for renovation and I don’t want new pastures overhwhelmed with thistles, nettles and other unpalatable – or even toxic – weeds.

The flats are rich, deep alluvial soils that retain moisture well during dry times yet drain well during wet times. They get us through summer and their pastures are always the quickest to recover but because the grass species are so old, quality is sometimes lacking.

Still, I’m a little reluctant to renovate them for a few reasons:

1. We rely on them being productive while our drier slopes are close to dormant over summer
2. They do flood and I don’t want to risk erosion
3. We need to be careful not to disturb the balance of soil life

The answer will be to temper my enthusiasm a little, take it gently, and renovate just a couple of our delicious river flat paddocks at a time.