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PostPosted: Tue Jul 22, 2003 9:25 pm 
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Location: DFW
Allelopathy
http://www.wm.edu/biology/bio405/allelopathy.html

I'm curious if any of you have had experience with this?

So far the only thing I have growing in areas, I might not should have, are sunflowers. Things are growing fine around them though. So go figure.

Plus I heard that any sunflower in my compost will not hurt anything after the winter passes, then the compost will be fine. I read that after a wintering the allelopathic properties will be gone.
Any views on that?

http://www.units.muohio.edu/dragonfly/itc/index.htmlx

Sorry if I picked the wrong place to post this. :wink:


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PostPosted: Wed Jul 23, 2003 7:25 pm 
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Location: Dallas,TEXAS
Wow! Now I know the name for the phenomenon I see around my bird/squirrel feedres - sunflower hulls do inhibit any kind of seed or weed growth except for their own! But - the name makes sense...I have not composted them for just that reason, but I have used them successfully as a mulch in between lettuce rows...
I will see what I can find out about it...........
drchelo


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PostPosted: Wed Jul 23, 2003 7:40 pm 
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I found two references through Google that address sunflower seed hull allelopathy...and here they are!
http://www.psu.edu/ur/NEWS/news/Gardening.feb24.htm and
http://www.wm.edu/biology/bio45/allelopathy.html and if these don't work, I went to Google, and typed in "Sunflower Seed Allelopathy" and there were a lot of others. But these two did address the issue of allelopathy after overwintering - and they indicate that a few won't hurt, but if too many stay behind in the ground, you may have poor plant growth in the spring..
Don't you just LOVE Google??
drchelo


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PostPosted: Wed Jul 23, 2003 7:43 pm 
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Thank you!
I have a "growing" curiousity on this subject. :D More so, some people's own experinces with it versus heresay on the net.

I have read a lot about what some say and what real gardeners have seen happen in their own garden. I want to know the tried and true, not the "oh this will happen".

I'm interested to see what you find out! :D

Like I said; my sunflowers are cohabitating very well with my other plants. Though no WEEDS have grown near them. My next year's flower beds and gardens are going to still have bunches of sunflowers.

Though I do know taking OUT the dead leaves and branches and putting them in the compost pile helps the flower/garden. Something about them decomposing.
Or do I? That's the problem!! :roll:


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PostPosted: Thu Jul 24, 2003 9:20 am 
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OK - here is what I found out from Texas A&M...there is a phytotoxin present in the pigmented part of the black sunflower seed. It is an alkaloid that is heat-stable that degrades only slowly with decomposition. On another site (A guide for science teachers student projects on effects of sunglower seeds) the suggested experiment was to use different numbers/concentration of substances in the planting medium.
Nothing that I have found to date tells me just what the allelopathic toxin IS - nor what will decompose it. The articles I read on crop rotation seemed to indicate that alfalfa (which also contains allelopathic agents) should NOT be re-seeded over a field which has been used that season for alfalfa because of reduced yields.
Anyway, I have put in a question to our County Agriculture Extension Office about this...and I will see what I find out! Sometimes these esoteric things are difficult to find just surfing the 'net - I may end up having to see what I can find in the real library!
But - I am like my bulldog. I will worry these things to death until I find out!
drchelo


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PostPosted: Thu Jul 24, 2003 1:34 pm 
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Quote:
It is an alkaloid that is heat-stable that degrades only slowly with decomposition


That's something I want to know much more about.
I'm very curious yo see what the County Agriculture Extension Office has to say. I do hope they reply to you in some way.

I know exactly what you mean about it being hard to find much on the net regarding this subject. I've spent hours and I still feel quite in the dark. You'd think people would more apt to put information out there about what they've dealt with. :roll:

http://www.units.muohio.edu/dragonfly/itc/index.htmlx
I appreciate your bulldog attitude! :wink:


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PostPosted: Sat Jul 26, 2003 5:09 pm 
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Well..I think I found out more about allelopathy than I think I can absorb...but the only identified and named allelopathic substance ("allelpathic"substances are grouped under the general heading of "secondary substances" that are different phytochemicals..) that I could fine in the English language literature available to me is "phenoxycarbolxykic acid"...these secondary substances are found in many plants - including the roots of corn plants, alfalfa leaves, stems of other plants. Bacterial action can decompose some of these - but "low tillage" soil preparation that is advocated for some organic farming techniqhes apparently leaves the subsequent crop more prone to allelopathic substances, as low-tillage soil soes not have as much bacterial activity as soils that are prepared differently.
I also found out all kinds of useful information...such as counting the number of root hairs on certain corn species can predict the allelopathy potential for that species..But I think I will stop before I bore you all.
The County Extension Agent asked me if I was crazy...
drchelo


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PostPosted: Sat Jul 26, 2003 7:54 pm 
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Quote:
The County Extension Agent asked me if I was crazy...


Well that's not good. :roll:
Maybe they need to do some homework. :lol:

The low tillage part makes sense to me. Thus maybe less concentrated in one area. Then easier to break down by bacteria and etc.

You are not boring me, this is fascinating information.
Thanks! :D


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PostPosted: Fri Aug 01, 2003 6:58 am 
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The allelopathy associated with sunflower seed hulls might do a fair job as a weed deterrent in places where weeds are difficult to manage, such as a fence row or maybe in paving. I don't know that it would have much effect on rhizomatous plants like Bermuda grass, but maybe it would help suppress it. Allelopathic plants apparently don't affect every other plant specie -- for example, see the list of plants that are resistant to black walnut at: http://www.johannsens.com/gardentips/wa ... icity.html The major grass suppression effect I see under my bird feeders seems to be from the birds' physical activity. Still, if one has an area where weeds are a persistent problem and if one has an abundance of hulls, that might be a way to use them. A few intact seeds could lead to a sunflower stand, though.

There is a fair amount of information about allelopathy in general on the Web, but most of it does not seem to focus on sunflower seeds specifically. Rye grass and black walnut are mentioned more commonly. If you have back issues of Horticulture Magazine, I seem to remember an article on the phenomenon in the Dec. 1998 issue, I believe. The allelopathic effect of rye grass raises the question of whether overseeding with rye prevents weeds by crowding them out, but allelopathy, or both. I imagine there is data on that question somewhere, but I suspect it is more the crowding than the chemical effect. The rye doesn't seem to affect the resident turf grasses, but then I believe the allelopathic agents in rye are different from that/those in sunflower hulls. It may be that, at the point in the southern growing season and in rye grass maturity when the rye recedes and the turf grasses begin to grow, the rye's allelopathy is not as active or effective. It also may be that the allelopathy is ineffective on resident plants like the dormant summer grasses, as opposed to seeds/sprouts.

I suppose a question arises as to whether the allelopathic components affect tree roots. Phenoxycarb was mentioned above as an allelopathic compound; it is an isomer of the herbicide mecoprop, and 2,4-D is in the phenoxycarb family, so I suppose that there is a potential that a very heavy dose of sunflower hulls might affect tree roots. It is not a coincidence that many synthetic herbicides were developed from allelopathic mechanisms/substances. I believe that free PCA is pretty soluble in water, whicih would mean that it leaches easily, but the dose in sunflower hulls is very small. I doubt there is anything to worry about with respect to trees, especially more mature trees; I could be wrong.

As an aside, for a peek at what is taught about pesticides (with your tax dollars and much pesticide industry support) in university weed/crop science courses, take a look at this exam:
http://www.cropsci.uiuc.edu/classes/cps ... m01-3.html

_________________
In theory, theory and practice are the same; in practice, they aren't -- lament of the synthetic lifestyle.


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PostPosted: Thu Aug 07, 2003 2:01 pm 
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Thanks Enzyme11! :wink:


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 Post subject: re: mecoprop
PostPosted: Thu Jul 01, 2004 3:48 pm 
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I thought mecoprop was an organic herbicide??

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