Mow-Killing Rye and Vetch – Will This Stuff Ever Die?

Oh, dear Roundup, you are so enticing!
We planted about 23 acres of a cereal rye and hairy vetch cover crop in September 2011.  It’s now late May 2012, and this stuff is still not dead!  We’re trying to kill it organically by mowing it at the right time (at flowering).  We mowed all 23 acres twice, and the vetch just keeps on coming back!  My go-to cover crop manual, page 71 says vetch does not bear traffic.  Not true, at least for this variety.  The vetch that got ran over by the tractor tires and therefore lay too low to be cut by the bush hog came right back with shock & awe gusto in a few days.  Vetch is a wonderful soil builder and nitrogen producer.  It’s a stellar cover crop, but it’s very aggressive in the spring and livestock don’t like to eat it.  So, we don’t want it producing seed and growing again in our future pastures.

Vetch mat in neighbor’s field. No rye germinated.

Another reason we want to kill it is so we can plant our summer cover crop mixture.   The new seeds need a good start with no vetch competition.  After mowing twice, we shrugged our shoulders and went ahead and planted.  We think the no-till drill (planter) we rented from our county helped with killing the vetch.  The drill has sharp discs that slice the soil surface like a pizza cutter to make a tiny furrow for seed placement.  So far, it looks like the pizza cutter action cut a lot of the vetch at ground level, which is probably what it needed to finally die.  Our bush hog mower won’t go lower than six inches.  We’ll wait and see if the vetch comes roaring back.

Mowing Would’ve Worked Better If…

…If the cereal rye germinated, dang it!  Cereal rye grows strong and tall, up to 6 feet high, and vetch loves to climb it.  Mow-killing vetch and rye is successful when the rye is holding up the vetch.  We know because the rye germinated and grew really well in parts of our 3-acre field.  The bush hog decimated the vetch where it was supported by rye stems, no need to mow a second time.  In our neighbor’s 20 acres, however, virtually no rye germinated, and the vetch just grew in a 3-foot tall dense jungle mat.  The bush hog has a hard time getting under the vetch mat to cut it off close to the ground and kill it good.

Rye Failure

Rye and vetch both grew well in our 3-acre field.

Why didn’t the rye germinate in our neighbor’s 20 acres?  The rye seed could’ve rotted by Hurricane Irene and Tropical Storm Lee’s 15 + inches of rain (vetch is a harder seed than rye).  Another possibility is nitrogen.  I’ve read that legumes will flourish in nitrogen-deficient soil because their symbiotic root bacteria fix nitrogen from the air.  Grasses (rye) are nitrogen hogs and don’t do well when soil N is lacking.  Our 3-acre field had been in pasture for 3 years and had quite a bit of clover.  Perhaps soil N was sufficient there.

Encouraging Signs

I love the sound the bush hog makes when it hits really dense cover crops!  VROOOM!  That means the clippings will make wonderful mulch to armor the soil from weather extremes and entice the beneficial tiny soil animals and microbes to make their homes in our fields.  The fields now feel like a big fat cushion when I walk on them, which is a great feeling and a sign of returning soil health.   The vetch also attracted some birds and insects that I’ve never seen in that high of numbers on our farm before.  The ladybug numbers on the vetch were amazing, and red-winged blackbirds seemed to be very attracted to the vetch as well.  I didn’t find either of these two in our grass pastures, which were right next door to the rye & vetch fields.

Another encouraging sign is nitrogen.  I’m super excited about this, because soil has to be at a decent level of health in order to provide nitrogen to plants naturally.  The soybean farmer that farmed our fields planted annual ryegrass as a cover crop for several winters.  Like vetch, annual ryegrass is notorious for producing lots of seed.  We have lots of volunteer annual ryegrass coming up after we mowed the vetch, and it’s dark, dark green and super healthy looking!  I’ve never seen grasses on our fields look this healthy.  I’m assuming it’s due to the big nitrogen contribution from the beneficial vetch root bacteria (Rhizobium).  Decomposing vetch vines also contribute some N.

What’s Next
Our summer cover crop cocktail is planted.  We expect it to grow really well following all the rye and vetch benefits. We’re planting diverse cover crops to entice a diverse beneficial bug community to our fields to work with biology to pump carbon (organic matter) into the soil.  The healthier the cover crop is, the more likely it will be to provide max benefits to our soil.  We’re excited to see how our new summer cover crop grows.
UPDATE June 1st

Killed vetch in neighbor’s west field. No vetch, but lots of volunteer annual ryegrass! Mowing twice (3 wks and 1 week ago) made vetch residue to break down faster and negated vetch mulch’s weed suppression.

Rich and Jeff mention in the comments about the drill’s discs (they’re called coulters!) do a nice job of cutting and killing vetch.  They’re right and here’s proof!  This first picture shows a green field – I mowed this field twice.  The vetch is gone, but look what’s taken its place – annual ryegrass volunteers!  This must be from past cover crops.  I mowed this field the first time 3 weeks before planting the summer cover crop.  I suppose the time lapse and the second mowing broke down the vetch residue so much that plenty of sunlight got in and encouraged the annual ryegrass to germinate and grow.  This isn’t the end of the world, but it’s not the best situation for the new summer seedlings.

The second pic shows what worked really well for vetch kill and weed suppression:  mow just once, then go ahead and plant using a no-till drill.  The drill’s coulters will finish off the vetch.  The vetch residue turns into a thick crunchy mat.  The new seedlings are coming up through it superbly.  Being not very high in carbon, the vetch mulch will probably not last through the summer, but it will provide good weed suppression while the new plants are getting started.  I’ll definitely use this method of one mow & drill coulter slicing to kill a viney cover crop like vetch again.  Saves time, fuel, and heavy tractor traffic on the field.

Killed vetch in neighbor’s east field. Killed by one mowing and then planting one week later with no-till drill. Drill’s coulters sliced and finished off the vetch.


2 responses to this post.

  1. Posted by Rich on May 24, 2012 at 10:46 pm

    I have a stack of old issues of Small Farmer’s Journal, and each issue usually had a column written by Anne and Eric Nordell where they they talk about their market garden and the techniques they use. I haven’t been able to find anything else available about their techniques besides these old issues and a couple of videos on YouTube (which is a shame because I learned alot from reading those columns).

    They plant a series of cover crops to build and maintain the fertility of their fields, and use different tillage tools and methods to kill and incorporate their cover crops.

    When they plant vetch or rye/vetch they pull a horse-drawn inline disc (similar to a coulter cart on a no-till drill) to cut up the vetch. They also use a sickle bar mower to cut up the rye, making one pass with the sickle in the transport position (up in the air), then a second pass with it down on the ground, followed by the inline disc to chop up the vetch.

    If you are interested, there is an article that might give you a starting point to look for more info at:


  2. Hmm- I thought of the Nordells too. As noted, they slice vetch with coulters. However, I would not be so ready to replace a nice stand of vetch. It is most definitely grazable. I frost seed it into the pastures every year. You need some mob grazing. That will seriously build your organic matter and jump start your soil biology. Good luck!


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