[APWG] Allelopathy Nasella straw Re: Pour on the mulch on annual weeds now

[Wayne Tyson]

All:

The grass-straw mulch is an interesting idea, and I certainly don't doubt 
that such a practice might have some utility in suppressing weeds, but I am 
concerned about suppression of indigenous species as well.

I wonder just which "allelopathogens" are responsible for the observed 
effects? What is their mechanism of action?

I worked with a MS candidate on allelopathy studies around 1969 or '70, but 
nothing conclusive was demonstrated. I observed what I was sure was chemical 
suppression of Salsola kali on a restoration project around 1973, but even 
after spending an afternoon with C. H. Muller, I could come up with no real 
answer. I still don't have one, but sure would like to know . . .

WT


----- Original Message ----- 
From: "Craig Dremann - Redwood City Seed Company" <Craig at astreet.com>
To: <apwg at lists.plantconservation.org>
Sent: Sunday, November 04, 2012 5:57 AM
Subject: [APWG] Pour on the mulch on annual weeds now


> Dear Wayne, Ty, and All,
>
> For those of us that contend with annual weeds, like California and our
> 1,000 species of exotics, and the Great Basin and their cheatgrass and
> cereal grains, now is the time to pour on the grass straw mulch.
>
> You can see a painting I did of my test plot, at
> http://www.ecoseeds.com/art3.html, and the yellow color is the test plot
> area.  I am using native Stipa (Nassella) straw mulch in one part of the
> plot, and the local weed straw in another part.
>
> If you cut the exotic grass straw in summer after the seeds have shed, it
> makes a nice local straw, but you have to put it down 4-5x as thick as it
> grows, because the exotic weed seedlings have a resistance to their own
> straw allelochemicals.  We had to harvest a ways up the hill to get enough
> exotic grass straw, to use in our plot.
>
> If you have the ability to mow annual weeds, instead of mowing, it might
> be better to cut and swath and then pile up a thick enough mass of the
> weed straw, to inhibit the growth of the weeds.  Certain weeds are going
> to need a thicker mulch than others.
>
> For example the Italian thistle and yellow star thistle needs a certain
> level, and the annual grasses may need twice or three times as thick
> because of their seedling resistance to their own straw.
>
> I am working towards 99.5% weed-seedling free test plots by December 31.
> I applied the first layer of straw a month ago, before the autumn rains
> started any seedling germination.
>
> About a week ago we got our first inch which gets weed seedlings to
> germinate, and I went out yesterday and applied two more bales of Stipa
> straw to cover whatever seedlings were growing through where the original
> mulch was too thin.
>
> In about 3 weeks, will go out and apply more certified weed-free mulch
> wherever necessary.  This use of straw mulch works well in areas wherever
> herbicides cannot be used, like in Endangered Species habitats, which are
> getting weed-infested by annual grasses or other annual weeds.
>
> For example, the Southern California K-rat areas in Riverside County with
> the annual grass weeds, or Desert Tortoise habitat in the Mojave desert
> where the Saharan mustard is swamping critical habitat.
>
> Hundreds of millions have been spent in California alone to buy land for
> the protection of Endangered Species, but almost nothing spent so far, to
> address the weed problems that are overtaking those lands.   Straw mulch
> may come to the rescue for those Endangered Species habitats.
>
> Sincerely, Craig Dremann (650) 325-7333
>
>
>
>
>
>
>
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