# allelopathy



## mulberrygrovefamilyfarm (Feb 11, 2009)

Just finished harvesting beans and found out that the alfalfa that was to be renovated and killed out by the roundup beans didn't get killed out. Guess I'm not a good bean walker. Anyway what's the thought about spraying it out when it grows a few more inches and trying to plant alfalfa this spring?

Checkout the alfalfa from this phone pic.


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## mlappin (Jun 25, 2009)

We never had good luck planting beans into hay stubble, could never get a good enough kill, or it'd be dry enough that the alfalfa already ate up the moisture reserve in the soil. Always had the best luck spraying it in the fall after the last cutting came off with 2-4d and roundup, then again in the spring and no-tilling to corn.

You can certainly try to replant next spring, might be a better bet to burn it down again and get some wheat planted instead.


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## vhaby (Dec 30, 2009)

The title of your post suggests that you already have an idea about the answer to your question. Planting alfalfa following the killing of an old alfalfa stand may not produce the desired new stand of alfalfa. The general suggestion is to kill the old stand and plow the soil. Then, plant another annual crop the following year. Work the soil after that annual crop to prepare it for seeding alfalfa the second year. Two years of annual cropping between alfalfa stands may be even better. Here is a web site the cites work by Dr. John Jennings when he was studying in Missouri. This article will give you more insight into allelopathy and alfalfa.

Alfalfa University

Once this site opens, you will need to highlight the text in order to read the black on dark green background. Hope this helps.


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## hay wilson in TX (Jan 28, 2009)

That is an interesting Link.

I have no doubt about allelopathy being real and a problem. Problem is I also believe my lying eyes and see volunteer seedlings in old stand alfalfa, that survive thickening the strand. 
What this is telling me is allelopathy is a true condition in alfalfa, just not a universal problem as mentioned in so many texts. I am sure it is a problem, because so many forage researchers have found it to be true for their University plots. 
I have not a clue why alfalfa does not kill alfalfa seedlings HERE. I understand a few other commercial growers also have found Autotoxicity in Alfalfa is not a problem for them. Again we do not know why just that it is an on the farm observation. 
I will insist that what ever Warren Thompson said on the subject is true for where observed.

Why is Autotoxicity not a problem in the Texas, Blacklands? Maybe it is in parts of the Blacklands, but it is not in our summer drought combined with our heavy vertic clay, high pH, calcareous soil. Why it is also not a fact of farming in parts of Nebraska , is a mystery to me.

Now to finding alfalfa (surviving) in beans may be other than it appears. What you see may not be regrowth alfalfa but new growth alfalfa. I find alfalfa in wheat fields, that been wheat following wheat, been sprayed with roundup at least three times, and plowed extensively. I believe this is not survival alfalfa but new growth seedling year alfalfa up from dormant or hard alfalfa seed. If this wheat field had only been sprayed with 2-4D I would have known if we had old growth or new growth alfalfa in a wheat field.

As a testimonial, I had a stand of Ram Alfalfa survive my poor management, and local climate 11 years. During that time it was treated as a seedling stand two different times, for the seedlings in the stand. That field would still be in alfalfa if the ground had not become to rough to hay.

In short, I contend Autotoxicity in Alfalfa regional phenomena not a universal phenomena.


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## mlappin (Jun 25, 2009)

I've heard from more than one person that autotoxicity does not become a real problem until you work the soil. Cutting the roots seems to be the key. I've notilled alfalfa right into thinning stands before with the success of the endeavor depending on the fall rains. Most of the time though like haywilson points out, I take em out as they are getting too rough.


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## hay wilson in TX (Jan 28, 2009)

Cutting the roots seems to be the key. 
I like that thought. I hope to be able to retain that idea.


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## mulberrygrovefamilyfarm (Feb 11, 2009)

Guess I hate to put the time and money into good alfalfa seed only to have a bad stand. I'm thinking I'd rather not "find out" whether I would have an issue HERE. I've got some oats laying around that I might as well sow in the spring, spray out the alfalfa, and pull a cutting of oat hay. Then I can go back to alfalfa. Thanks for all of the input.


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## UpNorth (Jun 15, 2009)

Autotoxicity is a huge issue and I would definitely rotate away from alfalfa for at least a year or two. The more tillage you do the quicker the autotoxic compounds will degrade. These compounds have their highest concentrations in the leaves of older plants and they are water soluble. They cause the roots to swell and reduce the number of root hairs.


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## rjmoses (Apr 4, 2010)

About 5 years ago, I had an 4 year old alfalfa field that was getting pretty thin. I took the 3rd cutting off of it, then disked it lightly, waited 3 weeks, then no-till drilled in about 15#/acre of the cheapest alfalfa I could find. The stand came up real nice, stayed healthy, gave me 5 more years. I question autotoxicity myself--it doesn't make sense to me from a evolutionary view--not that I understand evolution all that much.

As far as spraying it off with Roundup, I was told by an old farmer that most people spray it with too heavy of a concentration. It kills the top parts, but doesn't get carried down to the roots, so they grow back. He said it was better to spray it twice with 1/2 rate (1qt/acre).

Ralph

Ralph


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## mlappin (Jun 25, 2009)

We've found a pint each of roundup and 2-4d with a gallon of 28 per 10 gallons of water takes it out pretty well depending on plant size. I think a big part of that is getting it burned down in the fall after the last cutting, wait till enough regrowth to absorb the chemical, but not so much regrowth that the roots are replenished. If required a second application is made in the spring while the plants are still small.


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## JamesIII (Jul 25, 2008)

I had an "old timer" tell me he took off his last cutting in late August. Then he ran a straight chisel plow through it about 6" deep. 3-4 weeks later he chisel plowed again at a 45 to the first plowing, but about 12" deep. Then 3-4 weeks later he chiseled again just as deep as he could pull the plow. In the spring he seeded straight alfalfa and started harvesting in July. He said 6-8 weeks of tilled soil above 50 degrees soil temp. eleminated the allepathy affect. He raised near continuous alfalfa in central Iowa for many years. Never tried it myself, but interesting. James


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## UpNorth (Jun 15, 2009)

rjmoses said:


> About 5 years ago, I had an 4 year old alfalfa field that was getting pretty thin. I took the 3rd cutting off of it, then disked it lightly, waited 3 weeks, then no-till drilled in about 15#/acre of the cheapest alfalfa I could find. The stand came up real nice, stayed healthy, gave me 5 more years. I question autotoxicity myself--it doesn't make sense to me from a evolutionary view--not that I understand evolution all that much.
> 
> As far as spraying it off with Roundup, I was told by an old farmer that most people spray it with too heavy of a concentration. It kills the top parts, but doesn't get carried down to the roots, so they grow back. He said it was better to spray it twice with 1/2 rate (1qt/acre).
> 
> ...


So you got 5 more years out of the field, what did it yield compared to the first 4 years?


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## rjmoses (Apr 4, 2010)

The yield was about the same until this year. I'd have to check year-to-year This year, I had one cutting (about 3 tons) that got wet so many times, I ended up just putting it in a ditch!.

I'm not sure if age, insects (leaf hoppers got into it and I couldn't spray because of all the rain), or something else happened. I know it suffered some crown damage from having to mess with it when the ground was wet this year. And weeds were beginning to be a problem. It was also getting pretty thin in the high traffic spots, so I sprayed it off and put it into wheat. I plan on hitting it again with 2,4D in the spring.

It's a great field for alfalfa for this area, good drainage, not too steep. I'd like to rotate back to alfalfa/grass maybe next year.

Ralph


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## mulberrygrovefamilyfarm (Feb 11, 2009)

I may change my mind again... and again over the winter but I think I'm going to go with the regrowth try planting orchard grass after disking in the spring. If I get alfalfa regrowth, then all the better.


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## vhaby (Dec 30, 2009)

Here is a good article on alfalfa autotoxicity/allelopathy:

Alfalfa autotoxicity effects found to linger


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## hay wilson in TX (Jan 28, 2009)

That is the most inclusive article on the subject. 
At least there is a mention of a short wait in a couple of locations that I would not have considered. Though there is no mention of a volunteer thickening of alfalfa that is seen in a few locations. 
I am sure there is an alleopathy problem but the stated problem is not universal. 
The Universal truth is less obvious but we will know it some day.


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