RE: wood chips as mulch.
We’ve used wood chips extensively as mulch for trees and various garden plants for 15 years. Many years we’ve received 60 truck loads or more.
While there is some research which indicates top dressed wood chips can deplete N at the soil/wood chip interface There are generally few plants with a root structure that close to the soil surface. Wood chips should never be incorporated, unless the site is expected to remain fallow of desirable plants for a season.
Fusion, if you can find any links to the pecan research caused N deficiency by top dressing with wood chips, I’d like to read it please. Unless the pecan trees were brand new transplants, I can’t imagine an N deficiency by top dressing wood chips. As you know, pecans have very deep root structures. But every climate is different, and every soil is different, so I can only verify what I have seen in my climate with my soil.
My experience is that plants and young trees are substantially more vigorous with wood chip mulch in my climate, with or without supplemental N. This would be on non-irrigated plants and trees.
I suspect the mulch benefits (some mentioned by Fusion and Kris) outweigh any possible N deficiencies in most cases (i.e. water retention, less soil compaction, more overall nutrients, more mycorrhiza, soil temperature moderation, weed suppression, etc.)
My opinion is that wood chips start to break down so rapidly it would be difficult to produce an N deficiency in my climate. A load of wood chips which has sat on the chipper truck just a couple days is so hot it’s steaming when it’s unloaded, so the breakdown process seems to start immediately. After a heavy rain these wood chip piles will produce a visible “compost tea” at the base of the piles, which I suspect has supplemental N, since the most broken down part of the mulch will leach away first. My theory is with a heavy mulch pack, every time there is a heavy rain, the plants/trees get a small dose of supplemental N from the compost tea.
Dr. Linda Chalker-Scott has several good articles on arborist wood chip mulch. Below is one.
We use hay (occasionally straw) to mulch our tomato plants (we add no supplemental N to the tomato plants). The plants are almost overly vigorous even without supplemental N. We’ve observed the same with wood chips. Tomatoes are noted for shallow root systems, so N deficiencies should be more pronounced if there was a problem using wood chips.
One could argue that since we are applying it every year, the soil has banked enough N that subsequent wood chip or hay layers aren’t able to rob the soil of N. But even the first year applying wood chips or hay does not produce an N deficiency. We continue to add rows of tomatoes, so this has been observed many times.
Here is a pic I took a couple days ago where we are in the process of again adding mulch (this time hay) as a top dress to the tomato rows.
