How to stop weeds competing with crops
Handling competition in crops
.WEEDSMART week at Narrabri in the GRDC northern region is over for another year and the 140 odd attending persons went home with different thoughts and positive ideas about this focus on diversity of weed control.
As one of the organisers of Weedsmart week, we have endeavoured to gather a raft of practical speakers for this important issue in combating the herbicide resistance escalation.
My part was to talk about crop competition with a mixture of my experiences, visual photos and presenting some research data from great researchers like Michael Widderick and his DAF research team.
The array of photos I presented was solid evidence of more crop, less weeds phrase and proved that having an evenly spaced planting and crop germination operation was a major milestone in reducing weed numbers.
One of the many lines of research data I presented was in relation to narrowing your row spacing to reduce the ability of a weed like sowthistle or milkthistle to produce seed.
So moving row spacings in from 75mm to 25mm in this mungbean trial reduced weed seed production from 40,000 seeds per square metre to 17,000 seeds per square metre.
We can see similar weed seed reductions in chickpeas.
In fact their nickname years ago was chickweeds, based on the large amount of weeds growing in our now popular winter legume crop.
A replicated trial at Hermitage gave some impressive weed seed reduction figures.
Chickpeas growing on 50cm row spacings produced 70,000 sowthistle seeds per square metre. By bringing the row spacing into 25cm, the weed seed production dropped to 35,000.
So it halved in this instance and you can see this same weed seed reduction trend across all of our competitive crops.
Sure, still some very large numbers here, however when you introduce a Herbicide into this chickpea situation, the percentage control is impressive.
It is all a numbers game with our weed seed burden and yes, I fully realise this row space reduction may increase our foliar disease potential in those wet years like 2010 and 2016.
I even showed a photo from Central Queensland where an absolute over graze of buffel grass and leucaena, gave rise to a plethora of parthenium weed. Once again a crop competition display over hundreds of acres.
Similarly, with increasing the number of cereal crop plants per square metre like in our wheat or barley paddocks, the presence of weeds like black oats or ryegrass is massively reduced in numbers produced.
Yes, we do have many traditional reasons for having our wider row spacing or lower plant densities where they have been, however this herbicide resistance age is a big challenge to our min or zero till farming system.
So these simple practices of row spacing reduction and maximising crop plants per square metre is reducing weed seed production and therefore reducing our burgeoning and concerning herbicide resistance issues.
Think about it and give it a trial on your own farm, even just in those problem weedy blocks and sensibly compare your results with your agro.