Do cover crops actually help suppress weeds?

I did a bit of reading to try to find evidence to back up the idea that by growing a cover crop and creating a mulch which suppresses weed one could reduce or eliminate herbicide usage. One paper suggested that their cover crop mulch reduced weed numbers by 78% but had no effect on total weed biomass (i.e. each weed has less competition and so grew more vigorously). If one was using herbicides then this last finding might be useful. Reducing the density is useful because there are simply less individual weeds to kill, although perhaps if each is more vigorous the efficacity of the spray might be reduced.

So the question is whether it is a naive hope that cover crops can make huge inroads in reducing herbicide usage? Rather might they simply be one extra tool in a very large toolchest which is required to stay on top of problem weeds?

For: ... 1634365323 ... ;US9745251

Against: ... /410.short ... 2.0.CO%3B2 ... 10?LI=true ... 1634365323

Thoughts and experiences please!


DD Moderator
BASE UK Member
N Herts
Not more homework! I haven't finished Hands on Agronomy yet...
Rather lost the thread on the second 'against' paper (the wssajournal one) when they said they were harvesting 4.3 Million tonnes of biomass per hectare. Some cover!
Take this paper: ... 1634365323

It makes me wonder, if the cover crop is good at suppressing weeds, is it also good at suppressing the cash crop as well?!

Rye, for example, has allelopathic effects on weeds but there is also some evidence which suggests it does the same on the cash crop. Is it possible to somehow get the best of both worlds? I'm not so sure.

Cross slot boasts that it retains the cover over the seed row but might it not be better to actually give the cash crop some space so that it can actually grow?


BASE UK Member
I would have thought that there was quite a lot of evidence of organic growers using mulchs to cover weeds and let crops get away to say that it definately works. It does though I imagine work best with crops that are large seeded and rapid gowing that subsequently provide shading or their own allelopathic influence on the weeds when they come throught the mulch. So Pumpkins and maize work well. I think a cover crop of many species will help to reduce weeds by out competing them as well. Certainly that is my experience of using complex herbal leys in an organic situation.

CHAP Webinar - Innovative tools to overcome the challenges of Regen Ag

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Applying principles of regen ag can incur a range of on-farm challenges. Learn how innovative tools & machinery can help with these hurdles.

This event will be held online from 1pm to 2pm on Thursday 2nd December 2021 so please block it out in your diary.

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