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market-farming - Re: Horse manure/sawdust

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Chronological Thread  
  • From: Alex McGregor <waldenfarm AT sprintmail.com>
  • To: market farming <market-farming AT franklin.oit.unc.edu>
  • Subject: Re: Horse manure/sawdust
  • Date: Mon, 31 Jan 2000 15:51:24 -0500




Sojourner wrote:

> The belief that sawdust will "tie up the nitrogen" in your soil is a
> myth based on studies done with sawdust that had been "worked in" to the
> soil - e.g., was decomposing (or rather not) in anaerobic conditions.
>
> Spreading sawdust on TOP of your soil will not cause a nitrogen
> deficiency. Aerobic decomposition, taking place in the presence of
> oxygen (which is what goes on when you surface spread) is a whole
> 'nother animal than anaerobic.

It is true that adding any dead plant material to the soil will "tie up" the
nitrogen.
This means that the nitrogen is used by the population explosion of the soil
life that
happens when you add a lot of "food" for them. The nitrogen is still there-
just in the
bodies of the living microbes and they can out compete the plants for N.

Adding material to the surface as mulch slows down the decomposition and most
of the
"Feeding frenzy" is going on at the soil surface. This results in N in the
soil still
being available to plants.

As far as aerobic vs. anaerobic- plant material or manure buried too deep is
where
anaerobic bacterial breakdown happens. The byproducts of this process are
plant toxins
(formaldehyde being a major one). Burying it in the top of the soil where gas
exchange
happens produces aerobic decomposition. The byproducts of this are plant
nutrients.

So, the moral of the story is to bury cover crops, etc. as shallow as
possible and use
all the mulch you want.

Alex





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