[Adillo303]

I read that the sawdust from my dust collector can be used as mulch. There was a warning about black walnut being a herbicide.

Would anyone know how much it would take to cause problems, or is any amount too much?

I want to put it around my pond. I don't care if it kills the weeds and grass under it, just concerned about things around it. I don't use a lot of black walnut, but I do use some.

Thank you
Andy

 

[tc65]

I don't know that you could quantify an amount of sawdust = certain plants being killed. I would keep it away from any vegetable garden and other ornamental plantings, but I wouldn't be too concerned otherwise.

It won't harm all plants, certain ones are more susceptible than others.

Here is a short article from the University of Illinois Extension service talking about the effects of juglone on certain plants.

BTW - most of the juglone in a walnut tree is contained in the buds, roots and nut hulls - hence the reason that many plants have difficulty growing near a live tree. Much lesser amounts are found in the woody part of the tree.

 

[Bonka]

Sawdust

Sawdust will pull nitrogen to it and keep it there. My wife learned of this when she was working in a nursery.

 

[Sleeper]

Sawdust will pull nitrogen to it and keep it there. My wife learned of this when she was working in a nursery.

Ummm, I wonder if this would be the same for wood chips. This year I decided to use drip irrigation and covered the lines with wood chips to keep the water from getting too hot in the sun. My peppers are not doing well and I’ve suspected the wood chips as the problem.

 

[Adillo303]

Sawdust will pull nitrogen to it and keep it there. My wife learned of this when she was working in a nursery.

This bears some thought. I spread it on the dirt around the pond. I don't want anything throwing under it anyway. If it kills the grass and weeds under it great. I kept it six inches to a foot away from any shrubs or plants. I hope that is OK. I also understand that it deteriorates more rapidly than mulch.

 

[tc65]

Sawdust/woodchips are usually a problem when they are incorporated into the soil. Wood is a very high carbon source (as are other dried natural mulches). When a high amount of carbon is incorporated it throws the carbon:nitrogen ratio in the soil way off and will bind up almost all the nitrogen present. The only way to overcome that is to keep applying more nitrogen to help break down the carbon (combination of bacteria and fungi feeding on the carbon).

One key word here is incorporated into the soil. Mulch sitting on top of the soil will slightly affect the available nitrogen in the soil, but only in the very top of the soil. This will not have a significant effect on plant growth. I routinely mulch my garden with about 4" of a dried grass mulch and have no need for additional nitrogen fertilization. After the growing season I incorporate the mulch and it is broken down by the next spring.

My guess is that the wood chips are not the problem with regard to nitrogen fertilization as they are on the surface and peppers aren't an extremely high nitrogen user - comparatively speaking.