I'd use it for garden paths or in a perennial or shrub bed. The tie up of N could occur in the top inch or two and may affect shallow rooted plants or until the plants roots sink deeper.

tj

Thanks Mary and Tsuga. Maybe do a bit of each of your advice? Screen out through 1/2" hardware cloth, keeping the big stuff, then wait a month or so more until my maters(deep rooted) and peppers(relatively deep) dig in some more?

What do you think about that?

Kevin

Rule of thumb is that mulch is not a part of the soil. It covers and protects, but doesn't interact to any meaningful degree. Also, stories about un-composted materials tying up a lot nitrogen are specious. You have to work hard at it for that to happen, some people do, but it's not a big deal.

Toms are deep root growing machines. Mulch 'em to death with the stuff; don't dig it in, and it'll have NO chemical effect on the plants.

In a recent issue of Fine Gardening magazine was an article that told of what two researchers at Michigan State University found after 9 years of studying mulching and one thing they stated is that mulches, whether wood chips or straw or whatever, used as mulch (something put on soil not in), did not "rob" the soil of Nitrogen. They also stated that well mulched plants had higher levels of Nitrogen then plants growing in similar, but unmulched, soils.

kimmq is kimmsr

Evidently Colorado State still feels there's an issue...

" The use of fine chips or sawdust as mulch can tie-up soil nitrogen and can decrease soil oxygen levels."

Whole article

Sifting and keeping the bigger chunks for mulch would be best, but if you have a couple of yards worth that's a lot of sifting.

tj

tj: Indeed. But I wasn't planning on sifting the whole 2 yards. Just enough to mulch a 3x20' bed. The rest I can use like you mentioned earlier. That, and add quite a bit of the dust to a compost pile.

Thanks all.

Kevin

Copied from the article linked above, " When placed on the soil surface as mulch, wood/bark chips do not tie-up soil nitrogen. "

Seems to be contradictory statements within about 3 sentences.

kimmq is kimmsr

'Seems to be contradictory statements within about 3 sentences.'

LOL. just like the feedback on this thread.

Will use caution regarding the dust to ensure it doesn't become part of the soil.

One more question regarding the dust and small chips...If I were to till it in to a different area of my garden and use as an amendment, how long would I want to wait before planting anything so N tie up has passed?

Kevin

No part of the chips or dust is going to tie up any N. The N cycle is so prolific in most soils that industrial agriculture and intensive howe gardeners are the only folks tying up anything in the soil and have now become dependent on adding it.

If you like incorporate fertilizers/amendments into those beds during or at the end of season, then you'll want to pull the mulch off. If I was going to incorporate the big chunks I'd just plan on adding manures at the same time (probably in fall).

You certainly wouldn't destroy your soil by incorporating the big chunks but you put yourself in a position that would require you to till your beds every season to get the chunks to properly decompose the way you'd like. The tying up becomes more of and issue in your compost bin...

When tilling high carbon material into the soil you need about 6 weeks before planting (d3epending on how much was tilled in) so the soil bacteria have time to digest that material. The soil bacteria utilize Nitrogen when working to digest organic matter in soils and high carbon materials, such as sawdust or fine bark or wood chips, are such material.

kimmq is kimmsr

We are all going to assume you will be mixing this material in deep and wide and not putting a couple yards down in a small garden area. Without knowing the present soil organic matter percentage, no one can say that the soil's bacteria are going to be too busy using up the available N. Theres a great conversation about these issues in production agriculture and it applies to all soils, its the conversation with Dr. Albrecht about "insoluble but available" nutrients. The soil takes care of itself especially because the plant (and its roots) are present. All the bark chunks in the bags of "soil" sold from Lowes, Home Depot, Ace, and all the garden centers in between are not sapping all the N from their surrounding materials. The CO2 release into the soil would be the biggest concern aside from having big bark chips sitting there in the soil doing next to nothing until the microbes can slowly chew them up over time...

The idea about using the grindings as a soil amendment: It would work, but I wouldn't try planting veggies in it for a year. The breakdown-time will vary depending on your moisture/temperature conditions, but I would estimate a year will be sufficient. I work with coarse wood chips alot, and they can take multiple years to break down in the soil (depending on conditions).

A better idea (IMO): Plant a cover crop. Plant roots are A#1 the best for injecting carbon into the soil. Tilling in compost works fine, but it requires equipment/fuel, and it destroys the fragile-but-o-so-important microbial networks and soil colloids/structure in the process. I'm a huge fan of white clover. Deep rooted and nitrogen-fixing. When you want to plant a crop plant, just hoe the cover back with a sharpened hoe or spade. Yes it will want to spring back into your growing space, but honestly, any "weed" will find a way to reinvade cleared ground. Ideally, your plants will quickly get large enough to stand tall over the low-growing clover.

Save the stump grindings for mulch or the compost pile.

Cheers.

When I first moved here and was desperately trying to build up organic matter in my soil, a friend dropped off 8 cubic yards of aspen sawdust in my driveway. I spread it as mulch, 4-6" thick, around existing perennials in several flower beds close to the driveway. I was worried about the theoretical nitrogen tie up, so I threw a few handfuls of lawn fertilizer over the top. Meh - in retrospect, I don't think I needed to do that, but in any event, it all worked out fine.

Shane nailed it! Well said sir!

Cover crops are great in climates where there is regular rainfall. San Diego is a whole different story--average yearly rainfall is what, 10" at most? And the state is in extreme drought as well. Clover needs water. Please consider climate--it matters.

Use the stuff as mulch, just don't dig it into the soil. It will help your shrubs survive the long dry summer and water restrictions ahead.

Sorry, the OP was talking about mulching his/her veggie beds, so I assumed there would be irrigation available. It seems you might be talking about ornamental beds, in which case are there not indigenous low-growing plants adapted to your climate that could be imaginatively substituted for the clover? I think mulch only goes so far towards weed-suppression and soil-building while requiring yearly replenishment. Using a diverse living-mulch/cover-crop/ground-cover/plant-community is the next level of truly sustainable practice in any climate.

Cheers.

re drought - thats a good point. The best tool to deal with it is a thick mulch.