Bark Mulch
- To: perennials@mallorn.com
- Subject: Bark Mulch
- From: L*@aol.com
- Date: Wed, 15 Jul 1998 03:13:51 EDT
Peggy wrote:
>>It was my understanding that wood chip mulches only rob nitrogen from the
soil surface where the wood chips contact the soil directly, not
deeper in the soil around the plants' feeder roots. After the mulch
breaks down it returns the nitrogen back to the soil. I thought
nitrogen deficits were only of concern when incorporating wood chips
into the soil as an amendment or with mulching very tiny seedlings. Am
I mistaken?>>
No, Peggy, you are not mistaken. There is a lot of misperception about wood
mulches and it is perpetuated in many otherwise fine gardening books.
Wood mulch, fresh or otherwise, does not "leach" or "absorb" nitrogen from the
soil. It does not "rob" nitrogen from plants. What happens is that the mulch
attracts soil microorganisms. The microorganisms use nitrogen to break down
the mulch. So for a short time nitrogen is tied up. It is soon returned to
the soil when the microorganisms die. This is part of the natural nitrogen
cycle.
You are right, if the mulch is on the soil surface this process will not tie
up nitrogen in the plant root zones. Those roots are miles and miles away
from the soil surface in the tiny world of these microscopic organisms.
So mulch away without fear. You can add some nitrogen if it makes you feel
better, but I don't. --Janis
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