I'm finding the use of wood and wood products like sawdust in garden soil to be very interesting. The truckload of sawdust I purchased had supposedly composted for a year and was supposedly ready to amend my garden soil. It wasn't. It still had the appearance of fresh wood. It even smelled like freshly sawed wood with an occasional clump of horse manure in it.
The pile was in excess of four feel tall and it seemed impervious to penetration by moisture. I would sometimes check it after a heavy rain and find the moisture had not penetrated more than one inch into the pile. I had about decided to simply spread the pile over my pasture and let it rot away.
After about ten months of simply sitting in a pile, I noticed the pile had decreased in size by about 30%. I dug into the center of the pile and found that every grain of sawdust had changed from a raw wood color to a grayish brown color and it was all covered with a fuzzy fungi. Micelium had totally penetrated the pile and held the sawdust together in large clumps. No mushrooms were evident on the exterior of the pile, but the fungi were working hard inside the pile.
I am now using the sawdust again as a soil amendment and it seems to be working. My only complaint now is when the sawdust decomposes, it totally disappears. My beds which were amended with it the previous fall decreased in volume by the same volume of sawdust added. If I am going to use organics as amendments, I would prefer they last longer in the soil than the sawdust does. composted chips or even twigs or small branches may work for a longer period of time.
I've thought about using oak leaves but they don't seem to last long when added to the soil. My pasture is covered in a four inch layer of oak leaves which I can easily collect but I have noticed in the past they usually have rotted away by early spring.
Just my observations!