Win a copy of For the Love of Paw Paws this week in the Fruit Trees forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market private forums all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • r ranson
  • Anne Miller
  • paul wheaton
  • Jocelyn Campbell
  • Mike Jay Haasl
  • Burra Maluca
garden masters:
  • James Freyr
  • Joylynn Hardesty
  • Steve Thorn
  • Greg Martin
  • Carla Burke
  • Dave Burton
  • Pearl Sutton

Using sawdust (including from N-fixing trees) to build soil

Posts: 5
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I have a lot of sawdust from some recent stump grinding. Probably on the order of 10-15 cubic feet of sawdust. I've gained a LOT of information from this forum (and some extension pubs) about C:N ratios, how they work, why I don't want to just mulch with fresh sawdust because the microorganisms will tie up soil nitrogen and plants won't be able to access it until the bacteria die off.

I still have a few questions that don't seem to be answered by the posts I've found so far:

1. Some of the sawdust is from a mimosa tree (Albizia julibrissin), a nitrogen-fixer. The tree was probably 15-20 years old (unfortunately, it was half dead). Can I trust that the C:N ratio in this sawdust is lower? Any idea what it is?

2a. If I use a very thin layer (say, 1/4 to 1/2 inch) of sawdust sprinkled on cover crop seed as a top mulch to retain moisture for germination, will this have the effect of binding nitrogen and inhibiting germination or plant health?

2b. If the answer to #2a is yes, what about if I add some slow-release nitrogen fertilizer at the same time, so that now I'm top-mulching cover crop seed with a mixture of sawdust and fertilizer that has a C:N ratio of (say) 30:1?

3. Can I plant nitrogen-fixing herbaceous plants directly into fresh sawdust? Say, ladino clover? (my theory is no... but I thought I'd make sure.)

master pollinator
Posts: 8753
Location: Victoria British Columbia-Canada
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I would let the cover crop get a few inches tall and then lay the sawdust between the plants so there's no danger of matting and hurting germination. A nitrogen hungry product like sawdust is a good spot to sink nutrients from clover, vetch etc. I would mix it with coffee grounds and some dolomite lime to correct ph. The coffee gives up N slowly and is neutral acidity with no weed seeds.
Wait for it ... wait .... wait .... NOW! Pafiffle! A perfect tiny ad!
Food Forest Card Game - Game Forum
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!