With the removal of our trees (see this post) we gained a lot of organic matter (sections of trunk, branches, mulched twigs and leaves, wood chips from stump grinding): we asked to keep all of the material!
So our front yard has piles of this woody stuff which we are hoping to compost so that we can use it in an on the garden.
How do you compost wood products?
May be the first question is why do we want to compost this stuff?
- Nutrient Stability: If we put the wood products straight onto the garden, or dig them into the soil, they will begin to compost (naturally), which will deplete the soil of its Nitrogen reserves.
- Toxins: Wood is the storage place for the tree's toxins. When its composted in the ground the toxins are released into the soil. When its composted separately the toxins are released as a leachate.
When I was doing my Associate Diploma at TAFE we composted sawdust (quite successfully); but I can't remember the recipe and the book is packed in one of the many unpacked boxes in the boys' room!
I've done a bit of searching on the internet, found some good information at Compost Chemistry and found a couple of other recipes:
Making Use of Sawdust had three recipes, but as I didn't want to use other organic matter to compost the sawdust I chose:
Dilute 2.5 kg urea in water and spray onto or mix in about 150 to 170 litres of fowl manure for every cubic metre of sawdust. (A 2 gallon buckets holds about 10 litres.) Water the pile well and turn it a few times over the initial two weeks. Following this, the toxic phenols should be removed. There will be little nutrition in the composted sawdust, so add manure or natural fertiliser in the usual manner.
I estimated the pile to be about 4.5 cubic meters so calculated that I needed about 12.5kg Urea.
What I did remember from my TAFE experiment was that the micro-organisms just didn't need nigrogen, but just like us they need a balanced diet. Back in TAFE we fed them a complete fertiliser with a swag of micro-nutrients. But this wasn't "clean" sawdust either, it had bits of earth and leaf matter mixed in as well.
So what I decided to do was:
- 1kg 26-0-0 sulphate of ammonia
- 40kg of 10.1-3.5-5.5 general feriliser
- 5kg of 46-0-0 urea
- 1 bucket of ash from the fire place
Which should supply enough N and other elements to do the job. The reason for the sulphate of ammonia was that we had it on hand and we didn't have any of the other fertiliser available and I wanted to get the heap going.
Week One
We dug up all the woodchips from the stump grindings and barrowed them around to the back yard to a spot on a slight slope.
About one-third through we sprinkled some sulphate of ammonia on the heap, and then again at about two-thirds through. About 1kg of sulphate of ammonia in all.
The pile must be about 4-5 m3.