Bet­ter soil, fewer weeds

Her­bi­cide re­sis­tance linked to soil health


IT IS a dou­ble dish this week – spec­u­lat­ing on soil heath and her­bi­cide re­sis­tance.

What is the con­nec­tion there be­tween these two ma­jor im­pli­ca­tions for our farm­ing sys­tem?

Many years ago this same ques­tion came up in our south­ern and West Aus­tralian ar­eas with re­spect to acid type soils.

Not that we have many highly acidic soils in the north­ern re­gion, how­ever the con­sid­ered process should be ap­plied to your own cir­cum­stances.

The ba­sic premise is that crops grow­ing in un­healthy soil can­not com­pete very well with weeds.

Big state­ment, and I am not too big on bold state­ments like this, as some­where or some­one will prove you wrong, how­ever in this case I be­lieve that is a fairly safe as­sump­tion.

Ad­mit­tedly, for much of our information on these weed re­sis­tance is­sues, we are learn­ing from our West Aus­tralian cousins, who went through this dilemma with rye grass and radish in a bar­ley crop trial in low pH soils.

So for your knowl­edge, the trial was ap­ply­ing lime to their acidic soils to pro­mote good bar­ley growth.

We do know that lime ap­plied at up to two tonne per hectare and mould­boards ploughed into the soil ac­tu­ally dou­bled the bar­ley crop grain yield.

A good re­turn on in­vest­ment would be my judg­ment.

Wild radish plants per square me­tre on the other hand in this trial were re­duced by more than 50%.

A good re­sult for in­creased grain yield and less radish plants.

So the trial sum­mary read that the crop com­pe­ti­tion from the bar­ley grow­ing in a health­ier soil en­vi­ron­ment cer­tainly im­pacted and re­duced the radish num­bers per square me­tre.

We can make the as­sump­tion that while weeds do suf­fer from poor health in acid soils, our bar­ley crop suf­fered more.

So if your nu­tri­tional prac­tices are not as good as they can be for your crop and I in­clude ne­ma­todes in this thought as well, then your crop com­pe­ti­tion will not be as good.

That will lead to prob­a­ble in­creased weed num­bers and im­proved weed fit­ness, which will be to the detri­ment of your crop and a big­ger weed seed bank.

While we are still on this her­bi­cide back­ground to solve our prob­lems, we also need to im­prove our com­plete farm­ing sys­tem for bet­ter crop grow­ing and less weeds.

❝The ba­sic premise is that crops grow­ing in un­healthy soil can­not com­pete very well with weeds.

— Paul McIn­tosh


COM­PLETE FARM­ING: Bet­ter soil meant in­creased bar­ley yields and fewer weeds in a West Aus­tralian trial.

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