Three years ago a big oak tree on our property broke down and we had to have it removed. The tree service ran the branches that were too small for firewood through a chipper and ground down the enormous stump, and I left all those chips in a big pile for a year. Last year I spread the partly-composted oak chips as mulch about 3" deep in the pathways of my vegetable garden.
At the end of last year's growing season I plowed the oak chips into my garden along with some nitrogen fertilizer, and I did that again before I planted anything this spring. I was a little concerned that all that oak tannin would acidify the garden soil so I got a soil test this February that turned out fine - the pH was 6.8.
Now in working my summer garden I see that plowing all those oak chips into the soil was the best thing I could have done. There were a LOT of oak chips added, enough to cover the whole 35' x 50' garden three inches deep the year before. Now I can hardly find any oak at all, and my clay soil is much looser than it used to be.
When I do find an occasional oak chip in the soil, here's what they look like. The few chips that remain are being broken down completely by white root-like fungi that look like they'd be soft, but they're not. These soft-appearing white "roots" are hard and scratchy like the bristles of a stiff nylon brush. I bet by the end of this warm season I won't be able to find any oak in my soil at all.
If you ever have a chance to add oak chips to your garden soil this way, I think it's a real good thing to do!
