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Re: Re[2]: c-litter and weeds II



> As I recall, pigweeds have very small seeds.  It may be that they can
> pass through a chicken's digestive system and remain viable.
> Composting, with its assocaited heat, could kill the seeds in the
> manure.  Clearly, the first test is to see if there are viable seeds
> in the fresh manure.  Sounds like the perfect grad student project to
> me :)
> 
> TTFN - Eric Hanson
> Oregon State University
 
Further thoughts and observations: 

Pigweed is definitely a small-seeded annual.  However, it is
unlikely to be a contaminant of poultry litter because the 
poultry feed is composed of corn feed and soybean meal.  The 
primary source of weed seeds of raw manures comes from hay,
no?  More so, raw manures of large animals are the major
contributors of weed seeds rather than chickens which have gizzards 
to grind seeds.

Secondly, in the previous post, the practitioner-based
trials by the Luebkes found that immature compost
stimulated weeds while bio-mature composts did not.  It
should be noted that the immature compost had already gone
through the thermophyllic stage when weed seeds
are destroyed by heat and therefore it can be said that the 
manure-based immature composts were NOT a source of weed seeds
themselves.

Rather, the immature composts were immature in the sense that 
they had not reached a stage when humification had occured 
sufficiently to tie together short-chain, low-molecular weight 
compunds that are still water-soluble; whereas, the bio-mature 
compost had.   
 
Finally, it is these water-soluble humic substances and/or 
other biostimulants present in raw manures and immature
composts that come in contact with dormant-lying seeds in 
the soil and cause them to germinate.  

In the case of the pastures in Northwest Arkansas, though 
they were formerly in cropland, it has been several 
decades since cotton, corn, and other row crops were grown around
here.  That row crop weeds non-typical of a perennial pasture system 
would all of a sudden jump up and grow after a litter application 
but remain dormant after a synthetic fertilizer application
is all the more proof of the aforementioned scenario. 

Since microbes are intimately involved in these processes and resultant
end products, and since compost pile management influences the
activity of these microbes and degree of humification, there are often 
wide differences in compost quality.  Thus, farmers may experience 
quite different results in terms of weed populations, insect
and disease control, soil tilth, and soil fertility based on the 
spectrum that is raw manures-> to poor quality composts-> to good 
quality composts.  

Anyways, all this sounds like the perfect grad student/SARE research 
project to me too. 

Steve Diver
ATTRA - Sustainable Farming Information Center