Top Five Pros and Cons for Rye & Vetch Cover Crop in Veggie Gardens

Cereal rye and hairy vetch cover crop. Five feet tall 4/20/12

Not too long ago I was one of those people who knew a lot about plants but very little about soil.  I’d leave my veggie beds bare for the winter, not knowing what that meant.  After learning about soil’s needs, I started planting cover crops in 2011, and I’m so glad I did!

In late summer and fall of 2011, I planted cereal rye, a cool-season grass that makes rye grain, and vetch, a viney legume, in all of my veggie beds.  I inoculated the vetch seed with the nitrogen-fixing Rhizobium bacteria and then inoculated both with mycorrhizae.  Now it’s late April 2012, and it’s still alive and growing like crazy!

Here’s what I learned:

#1 Rye and Vetch Change Soil Drastically (PRO)

When I dug out bermuda grass (and a lot of trash) to make my veggie beds, the soil was dry, hard, and dusty.  I knew it would take a long time to reach the desired chocolate cake consistency – dark, moist, spongy, and smelling good and earthy.  With the rye and vetch cover crop, it’s almost there, and a huge difference from last summer!  The soil underneath the cover crop is very soft and spongy with beautiful aggregates.  This good structure will allow veggie roots to grow rapidly and air and water to percolate down into the root zone.

A great gardening goal is to always have something green and growing.  No bare soil!  Plants feed beneficial microbial soil life through root exudates.  As this cover crop was growing, it leaked a lot of sugary carbon compounds out of its roots to attract and feed microbes.  These bugs made the gums, glues, and gells that form soil into that chocolate cake consistency.  Bare soil has no living roots to maintain beneficial microbes at high populations through the winter.  Keeping soil life alive during the winter improves soil and ensures it’s ready to help veggie plants thrive in the spring.

#2 Plant-Available Nitrogen (PRO)

Nodules: Rhizobium bacteria fixing nitrogen on vetch roots. From http://ryansgarden.com

Instead of using synthetic nitrogen or expensive organic nitrogen inputs, why not grow vetch?  If inoculated with Rhizobium bacteria, the Rhizobium will fix nitrogen from the air and put it into nodules on vetch roots.  Isn’t that the coolest thing?  This handy cover crop reference says,

“Few legumes match hairy vetch for spring residue production or nitrogen contribution.  […] Hairy vetch delivers heavy contributions of mineralized N (readily available for the following cash crop).  It can provide sufficient N for many vegetable crops, partially replace N fertilizer for corn or cotton and increase cash crop efficiency for higher yield.”

That’s a whole lot of nitrogen!  And it comes at low expense with many other benefits.

#3 Weed Suppression and Free Straw Mulch (PRO)

Rye and vetch mulch drying down after cutting

No weeds here!  The cover crop’s outrageous growth in early spring smothers weeds by completely blocking sunlight.  I’m aiming for mostly no-till, so I’m cutting the rye and vetch off at its base.  This is generating a boatload of mulch!  Vetch mulch has a high nitrogen to carbon ratio, so it will decompose readily.  But rye straw at this late stage of growth (flowering seed head) has a lot of carbon, so it should last well into late summer.  This thick mulch will protect soil, keep soil temps cool in the summer so biology can thrive, hold in moisture, and prevent dirt splatter onto veggie plants.  And it’s free and organic!

#4 Beneficial Predators (PRO)

I’ve noticed a very big and diverse above-ground soil life community in the rye and vetch.  Loads of tiny mites, beetles, crickets, spiders, and ladybugs.  The diversity and populations are larger than I’ve ever seen in my garden.  The handy cover crop guide cited a study that showed a rye/hairy vetch mix sustained a population of aphid-eating predators that was six times that of unmowed volunteer weeds and 87 times that of mown grass and weeds.  I’ll take it!  Let’s get our predator populations really going and save ourselves loads of time this summer killing harmful bugs!

#5 Bad Timing for Early Veggies (CON)

Flowering cereal rye can be mow-killed.

Rye and vetch can be killed any time with herbicides, but organic gardeners must be patient.  Vetch can be killed organically when it flowers (late April/ early May in East Coast zone 7).  Cereal rye can be killed organically when it flowers around the same time.  (Flowering grain means the seed head is developing and the little stamens (anthers?) start to come out and drop pollen.)  Rye and vetch will die at this time by mowing or just knocking it down flat at its base.  No herbicides.

But you want to plant peas and lettuce and radishes in early March?  Whoops!  Not gonna happen unless you till in the cover crop or use herbicides, both of which I don’t want to do.  You can keep cutting it down at ground level, plant your peas, and then keep cutting the rye back, but rye REALLY wants to live at this stage and will stunt your early crops.  I tried it.  I did not try acetic acid sprays, which is another option.

This situation requires better planning in the fall.  I’ll need to designate beds for early spring veggies, and plant winter cover crops that will winter-kill (die on their own from hard freezes), such as oats and radishes.  But for later-planted summer crops like tomatoes and peppers, I’ll definitely plant rye and vetch again.

Seed Sources

If you don’t have a local source, search online for “rye and vetch seed for sale.”  High Mowing Seeds sells five pound batches for about $20, plenty for a 1,000 sq. ft. garden.  Think of all these benefits for such a low cost!  Thanks for reading!

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7 responses to this post.

  1. Posted by Rich on April 21, 2012 at 6:05 pm

    Years ago, I bought a 50 lb. bag of deer food plot mix at the feed store to plant as a cover crop in the garden. It was a mixture of wheat, oats, rye, Austrian peas, alfalfa, and crimson clover, and only cost about $20 (of course, that was back when a bag of chicken feed was about $5.00). It would be covered in the spring with lady bugs and honey bees.

    That bag would usually last about 3 years for a 2500 sq.ft. garden (I stored it in the freezer to keep the seed viable).

    But, now I just buy bags of whole oats or wheat (about $12 for a 50 lb. bag) to plant in the garden. The last time I was in the feed store I even noticed that they were selling bags of rapeseed (or canola) and buckwheat for a relatively reasonable price, so if you look around and get creative, you might be able to find an inexpensive source for garden cover crops.

    Another idea is planting something like blackeye peas from the grocery store as a summer cover crop (at less than $2 for a pound of seed).

    And, I once grew the best watermelons I’ve ever grown by flattening down a cover crop of winter wheat when it was in the dough stage (just starting to die down) with a board and a piece of rope like I was making a crop circle. Then I planted the watermelons into that thick mulch and they grew like gangbusters. If I am remembering it right, I also didn’t have as many squash bugs that year. It makes me wonder why I don’t do that every year.

    Reply

    • Posted by Rich on April 21, 2012 at 6:10 pm

      After thinking about it and in case you didn’t already know, most canola (rapeseed) is probably some sort of GMO (Roundup Ready or Liberty Link), so if that concerns you you might want to steer clear of buying a bag of rapeseed at the feed store.

      But, rapeseed is still an interesting plant as both a cover crop and cash crop.

      Reply

      • Good point – i try to stay away from canola. I did buy some bags of dwarf essex rape and camelina to plant in our summer cover crop cocktail for our fields. Will be my first experience with oil seeds and brassicas. I’ll post about that in 2 weeks or so, whenever the vetch in our fields finally blooms so we can mow-kill and then plant! We’ve had a very dry spring, so i wonder if vetch blooming has been delayed due to dryness. No delay in rye flowering.

    • Hi Rich! That’s a nice watermelon story. You should do that every year! 🙂 There must be lots of good stuff we don’t know about going on in the root zone with plant diversity. I’m excited to see what this cover crop can do in terms of yields/quality for my summer veggies. I read somewhere that rye/vetch is extra beneficial for tomatoes. At the very least, i’m expecting a low to nil aphid problem this year. Ladybugs adults and larvae must LOVE rye and vetch – they’re everywhere!

      I’m a big fan of buckwheat too. Used it last summer to fill in bare spots. It went to seed a couple of times, but looks like rye/vetch prevented it from growing this spring. Have lots of buckwheat seedlings in walkways, but none under rye/vetch. Probably starved of sunlight!

      Your deer food plot seeds – i will definitely add more diversity to rye/vetch cover crop next fall. At least some brassicas thrown in there. When/how did you kill that cover crop? Did it all flower at the same time?

      Reply

      • Posted by Rich on April 22, 2012 at 2:29 pm

        I’ve always thought that the ladybugs are able to more easily overwinter in the cover crop and what you are seeing in the spring is actually an increase in your ladybug “herd”.

        I never followed any set routine for killing cover crops in the garden, it all depended on how it was growing, the weather, and my mood at the time.

        When I was growing the food plot mix, I would usually just let it grow until spring, mow it, and till it under. Sometimes, I might have mowed it once, let it grow a week or so, then mowed a second time before tilling.

        At times, I tried just tilling without mowing, and if the tines on the tiller weren’t worn out, it would do an OK job (although I always planned on stopping a few times and cussing while untangling the grasses wound around the tines). If I mowed before tilling or just tilled, I wanted to leave a pretty rough surface anyway since I wanted it to break down a little before I came back and tilled right before planting.

        I think the Austrian peas usually flowered early (Feb-Mar.?), the crimson clover flowered around Easter, and the alfalfa doesn’t flower until summer.

        One time, I planted some food plot mix in an area I planned to plant peach trees and let it just grow until summer, then mowed the area. The crimson clover (and wheat and rye) made enough seed to produce a thin volunteer stand the next year, so I just let it flower and waited until the seed had dried down, then I mowed it again (I always lift the “deflector” on the deck so it throws the seed further). I do that every year and the clover stand keeps getting thicker and bigger, while I grow nitrogen for the trees and attract bees to the area without any tillage or seed expense. There should be a way to expand that idea to the farm on a much larger scale, but I’m still working on it.

        My wheat cover crops are usually mowed a couple of times over the winter, so the roots die back and regrow, etc., and are then just mowed and tilled at different times depending on what I plan to plant in the area (or are made into crop circles)

  2. Kelly, I’m also in zone 7 (in PNW), and I think one other answer to the early veggies question is simply to start seedlings in the greenhouse that can then be planted into the mulched beds later–just pulling aside the mulch where I’m planting. I should try that. 🙂 Usually I follow a Steve Solomon tip of fall-spring cover crops on beds that are getting summer crops the next year, and the early veg go in beds that had late crops on them the fall before, with some compost or straw/leaves over the winter. But I think there’s a better way!

    I had big plans for cover cropping last fall, but I also had grand plans for letting the chickens roam free in the garden through the winter. The chickens won! Too bad, because when I look at your mulched beds, I also think the chickens would LOVE all those bugs hiding under the deep cover… I’ll have to think about a better rotation system!

    Really enjoying these posts, and came over from NWEdible–thanks!
    Toni@BackyardFeast.

    Reply

    • Thanks Toni! Oh yeah i bet chickens would indeed love all the bugs. i’ve got tons of crickets and earthworms under there.

      I’m pretty set on trying tillage radishes and oats this fall in beds that will have early veggies. Both should winter kill in early Feb here. Oats will provide lots of straw for the growing season and i’m learning that radishes can do neat stuff for soil. The tillage type radishes can “bio drill” through a hardpan over 3′ down, among other benefits.

      i agree a straw/leaves winter cover is much better than nothing, and living roots are even better. I’ll check out your site!

      Reply

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