Oats as a cover crop?

I'm thinking about using oats this fall as a cover crop to fill in the gaps in my gardens prior to the approach of winter.

I've heard that oats winterkill, which is desirable to me for ease of spring planting. I have also heard that oats have a decent fibrous root system that will both hold together the soil as well as drill down to some degree depending on soil composition. What I'm incredibly interested in however is the fact that oats will form bonds with mycorrhizae, keeping a living root in the soil will hopefully maintain some fungal dominance in the soil to overwinter.

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Oats (80 Days Growth)

For those who have or currently use oats as a cover crop, what have been your experiences? Anything to watch out for?

Oats work well for this. I've used them the last couple of autumns and they reliably winterkill here, so spring cleanup is just pulling off the matted dead growth. Root system is decent for a cover crop, not particularly deep, but enough to hold the soil together and break it up a bit. Main thing is to sow them early enough that they get established before first frost, otherwise they won't bulk up much before dying back.

More academic experience than practical--oats for sure are good hosts for mycorhizal colonization which will benefit your soil.  Additionally, the roots of oat produce avenicins which are compounds known to suppress certain disease-causing fungi.  So you will get a multiple benefit here from the organic matter, soil conditioning, mycorhizal build-up and disease suppression from an oat cover crop.

I think oats would probably overwinter here fine as we don't get that cold (wikipedia suggests they are harmed by sustained cold below 7 Celsius) I have grown them as a spring sown crop and they do seem to improve the soil 'crumb' significantly. I gather the root exudates are really good for the soil bacteria too. If they don't winter kill you might have to dig them under and leave it several weeks before sowing. I'm not sure if, like grazing rye, the decaying greens are allelopathic?

I have seen oats go to seed and come back the next year, so that could be a minor drawback. We have a few acres of oats that were harvested a couple of weeks ago. A lot is growing back and if it's a late fall might even go to seed again.

Thom Bri wrote:I have seen oats go to seed and come back the next year,

Ooh! - is that perennial oats? Or are they just reseeding? Normally the plants will die after flowering.

It looks like progress is being made on developing perennial oats & other crops: https://landinstitute.org/events/kernza-field-day-practical-farmers-of-iowa/

Ac Baker wrote:It looks like progress is being made on developing perennial oats & other crops: https://landinstitute.org/events/kernza-field-day-practical-farmers-of-iowa/

I think that is just perennial wheat (Kernza) they don't mention the oats being perennial (although the bundleflower research of the same site also looks interesting).

Thom Bri wrote:I have seen oats go to seed and come back the next year, so that could be a minor drawback. We have a few acres of oats that were harvested a couple of weeks ago. A lot is growing back and if it's a late fall might even go to seed again.

I have heard/seen it myself. I believe timing will be important in order to make the winterkill effective, otherwise I may have to intervene if seed starts to set. The areas that I am going to seed should be limited enough that, if I had to, I should be able to manually chop and drop the material.

I'm sure if I plant for the average frost date, we will either get frost wildly earlier or later this year just out of spite!

Nancy Reading wrote:

Thom Bri wrote:I have seen oats go to seed and come back the next year,

Ooh! - is that perennial oats? Or are they just reseeding? Normally the plants will die after flowering.

Not perennial oats, just normal field crops. But quite a lot will attempt growing again. These plants die in the winter. What regrows the next spring is from seeds that fall. Or at least so I believe, not having actually tested this.

What time do you plan on sowing oats? They need 5 to 8 weeks before first frost to get established. The challenge for me is that in recent years, we tend to get summer drought and the top 1 ft of soil is bone dry. We don't see a period of slow and steady rain later in fall, making it too late to sow oat but rye would be fine. I can try fencing off a smaller area and water with a hose to help the seeds germinate. Oats cost $12 in a 50 lbs bag from feed store so it's very economical if I just broadcast a large area.

I've used oats as a winter cover crops twice; they didn't winterkill either time, but the people at the place that sold me the seed said it's a variety used for feeding deer, so they want them to survive winter. I'm in West Virginia, zone 6B or 7A. So I fed the grain to my chickens and used the stalks for mulch.

John Weiland wrote:<snip> Additionally, the roots of oat produce avenicins which are compounds known to suppress certain disease-causing fungi. <snip>

John, which fungal diseases are suppressed by avinicins?

I wonder if one might target specific fungal diseases  via oat cultivar selection, if given specific avinicins content of oat varieties.

May Lotito wrote:What time do you plan on sowing oats? They need 5 to 8 weeks before first frost to get established.

That is the million dollar question! My frost dates have been wildly inaccurate the past few years so I feel like I'm gambling no matter when I plant.

My back of the hand math is leaning towards planting earlier than later. The reason behind it is that my last few attempts at fall cover cropping have been leaning towards the late side than the early side. I'm sure this is only going to ensure that I get seed heads if I am not careful but I think that would be a good problem to have. Better than not having the biomass at all!

I however have to keep an eye out for my local chipmunk population. They sure do love oats and I'm sure will pounce at the chance to stock up on them prior to winter.

May Lotito wrote: Oats cost $12 in a 50 lbs bag from feed store so it's very economical if I just broadcast a large area.

12 bucks per 50 pounds?

Lucky you!  $29 for 50 pounds seed oats in my region!

Brian Cady wrote:

John Weiland wrote:<snip> Additionally, the roots of oat produce avenicins which are compounds known to suppress certain disease-causing fungi. <snip>

John, which fungal diseases are suppressed by avinicins?

I wonder if one might target specific fungal diseases  via oat cultivar selection, if given specific avinicins content of oat varieties.

Perhaps the most well-tested and well-controlled root fungal disease is the 'take all' disease of wheat which in the US is most prevalent in the Pacific Northwest.  The fungus is called Gaeumannomyces graminis var. tritici.  Although the avenacins (my bad on original spelling) are a well-studied chemistry within the saponin content of oat root exudates, the literature on the beneficial effects of oat pre-cropping in reducing disease suggests there is more to the story.  Additional saponins found in oat roots and elsewhere are known to be inhibitory to oomycete zoospores...oomycetes like Pythium (causing seedling 'damping off' disease) and Phytophthora (of which the dreaded 'potato late blight' is a member).  Moreover, there are actually several groups of fungal plant pathogens that are capable of detoxifying avenacins and reducing or eliminating their effectiveness.  Combined,  some other factors therefore must be contributing to the oat pre-crop effect at helping to reduce disease in many crops planted after the oats.  

As for your second question, I don't know how much this has been investigated.....digging into the cultivar or heirloom accession of a pre-crop (oats, radish, etc.) to see if there are those that specifically control one disease or another in the following crop.  What has been known for some time now is that certain genetic variation in crop varieties will do better with some *strains* of a biocontrol bacterium.....think Bacillus thuringensis or 'Bt'..... than with other strains of that same biocontrol agent.  The corollary is that it is likely that different oat varieties should condition the soil differently and may affect the incoming crop in a different way.  And always worth noting that the different pre-crop species (oat vs radish vs some other green manure) will not only be producing different chemicals against pathogens, but also recruiting different populations of potentially beneficial microbes.  So the (research) plot ever thickens!  :-)

Oats will do...
And, rye will give you considerably more root depth and total biomass, below and probably also above ground.
However probably won't winter-kill, this link from University of Vermont mentions using oats instead for that purpose:
https://www.uvm.edu/vtvegandberry/factsheets/winterrye.html

A bit more on rye:
https://soilandhealth.org/wp-content/uploads/01aglibrary/010139fieldcroproots/010139ch6.html

A classic biointensive compost/cover crop mix is winter rye, winter wheat, vetch, and fava.

I can vouch for this combo in the Pacific Northwest from when I had a biointensive garden in Seattle. The rye for sure produces a LOT of root mass, and deep.
None of it winter-kills in that climate of course. Which is good if you want max biomass for compost, but your case is somewhat different if you want the reduced work from a winter-kill.

I (25+ years ago)  put in a new lawn after having a house built.
I planted plain oats with the EXPENSIVE perennial grass seed to act as a nurse crop.
(If I do it again, I'll spread clover seed too.)
The oats gave good shelter for the tender lawn seedlings, prevented erosion during and after their life-cycle.
The next year, I had an acceptable start to my new lawn.
For what it is worth, I did not know where the sidewalks were going to end up so I made paths with pallets. The grass /oat seeds grew between the slats and I could chose my sidewalk placement later.