Bark Mulch a problem? Nitrogen? Acid?

(Carisa) Raleigh, NC(Zone 7b)

I just made a new bed and was looking around at different types of mulch because I have decided to go in a different direction this year with mulch and found this article.

It basically says that "bark mulch" isn't good for your soil because it doesn't have enough Nitrogen, so when it breaks down, microorganizms end up using all of the nitrogen out of the soil, therefore depleting it for your plants. What do you think about this? I was thinking about hardwood mulch this year, but this made me stop and think about it further.

I have also considered pine needles as a mulch, but read that they can be acidic. Just trying to make a choice that will block weeds and look good, aesthetically, but not do any damage by depleting or adding bad stuff to soil. I already have clay soil, so don't need anything that makes it worse! I have read through several threads about what others use, but the nitrogen issue doesn't seem to be mentioned. Thanks so much!

Charlotte, NC(Zone 7b)

I've read so many conflicting statements about using/not using bark/pine needles that I hesitate to say which way is "best."

When I lived in Tennessee, pine needles were free for the gathering. I used ample amounts, and the only thing that failed in my garden were beets. Can't say whether or not it was caused by the pine needles.

As to bark - if you are concerned about them robbing the ground of nitrogen, add a little blood meal to them. Not too much, or the blood meal will kill your plants. Too much nitrogen is not a good thing.

Anne Arundel,, MD(Zone 7b)

Buy what you like.

Here's my two cents;

I think one study was published year ago, and hundreds of writers have repeated the nitrogen robbing thing all over the place. And every commercial planting I see is swathed in inches of shredded hardwood mulch and looks fine with no further attention. Go for articles at Extension Services and arboretums, don't put too much faith in run of the mill blog writing.

All barks, wood chips, brown stuff are going to be pretty close in content. The size of chunks or pieces and their geometry , both affect how quickly it wants to decompose. Bigger chunks have less surface area for bacteria to attack. THey would be slower to decompose and would support less total bacteria for stealing nitrogen.

Something I recently read via a link here somewhere- said that part of the effect of mulching IS the nitrogen robbing effect of heavy carbon on the soil surface OK I can buy that. So do not use lots of mulch around tiny seedlings, but go ahead around bushes.

(Carisa) Raleigh, NC(Zone 7b)

when I read about the nitrogen stealing my first thought was wouldn't my annual manure application pretty much solve that?

Enterprise, AL(Zone 8b)

I think sallyg is right on the surface nitrogen, if that material was tilled into the soil you might have a nitrogen problem but then the manure you add would probably take care of that also.

Everett, WA(Zone 8a)


>> wouldn't my annual manure application pretty much solve that?

I think, yes. Even if wood or bark are turned under the soil and mixed in, if you add (or the soil already had) sufficent N to feed both the stimulated microbes and your plants, there is no problem.

Some websites twitter about how hard it is to "balance" added N with the increased uptake requirement, but I doubt that unless you add a lot of fine sawdust (that would try to suck up a lot of Nitrogen very fast.

A few coarse chips or nuggets will only stimulate slow uptake, and slow-release manure ought to balance that out.

Or add a very little chemical fertilizer every few weeks. maybe plants will not have absolutely optimal N levels every single day, but big deal. If your soil is hideously bad clay that floods and stays anearobic for days, that counts for a lot more than fluctuating N levels.

However, I woukld lean this way: if I was going to turn any fine wooden sawdust under, I would compost it first. Why not?

If I was going to turn under very much finely shredded wood, I would compost it first,

BTW, the one time I used a lot of a really cheap woody "Soil Pep" amendment that was all coarse wood shreds, I got huge amounts of some powdery underground fungus or mildew and the bed was really wierd for a year. It wasn't N deficiency as far as I can tell, more like "Invasion of the Fungus Monster".

That experience soured me on ever using un-composted wood as a soil conditioner. But I bought a cubic yard of medium-fine shredded bark with plenty of fine bark powder, and used lots of it raw on c lay and crushed rock with good success, adding barely more than one inch of compost but spreading 16 oz of chemical fertilizer over some hundreds of square feet every few weeks. That was way too little compost, but all my budget and little pile provided. The bark provided much of the OM over the next few years, and I added an inch or so of compost per year (still not enough compost for GOOD soil, but enough to support plants while I continued improvin g the soil and making more beds.

Everett, WA(Zone 8a)

I've heard people quote writers worried about pine needle acidity.

I've read experienced writers and people who use lots of pine needles not having any acidity problem at all.

As a kid, my compost heap was 90%+ pine needles. It did seem to like a little lime, but that was one huge heap of pine needles and almost nothing else. Where it got it's N, I don't know. That's probably one reason it cooked slowly!

My guess would be, if you're worried, use a little limestone or Dolomite limestone, and then wonder WHAT acidity problem?

Ditto for coffee grounds. WHAT acidity problem?

This message was edited Mar 15, 2013 6:43 PM

(Carisa) Raleigh, NC(Zone 7b)

This is all very interesting, thanks for the feedback. I'm not planning to turn it under, per se, just a top dressing for looks. It will work itself in on its own over the year(s). Clay soil is such a pain in the first place, I just REALLY didn't want to be adding to the problem, you know? Looks like it's not that big of a deal, with the top-dressing of manure that I do each year. I have noticed that the local soil place that I get the manure from also sells compost. Maybe I will add that to my regimin as well. I do the manure in the Spring, of course. What's the best choice for the compost. Mixed in or at a different time of the year? Or should I do one one year and one the next in the Spring? Thanks for your help. Changing what you have done for years takes more thought than I anticipated!

Charlotte, NC(Zone 7b)

Rick - You need not [u] [/u] (doesn't matter if you use upper or lower case. :)

Anne Arundel,, MD(Zone 7b)

(Ric use a lesser than and greater than sign, on the comma and period keys, instead of a [ ] and you will get your effect)

Charlotte, NC(Zone 7b)

Rick, I had typed a < and a > but they didn't show up. Do what sally said. LOL

Everett, WA(Zone 8a)

Thanks for reminding me! I should always check, but often forget.

My belief is that "any time is a good time for compost".

"Spring and fall" is best if you have plenty of compost.

"Right before planting" is probably best if you only have a little available.

Mixing finished compost into the row you're planting is great, but top-dressing is OK if there's a reason not to turn the soil (or if it's just not your policy to till). Just rake the pine straw mulch ASIDE before you top-dress with compost or AGED manure. It should touch the soil so it stays moist and worms c an be attracted toot it.

Probably it is NOT as good an idea to turn raw manure or completely un-composted browns under the soil right before sowing or transplanting, Compost them first instead of making rootlets deal with hot manure or dry straw.

Or spread raw manure plus whatever on top of soil in fall, so it will sheet-compost before spring.

(I like turning the soil, and mixing in the compost is a good excuse. When I get a bed into really good health and enough organic matter, I don't till it until the OM has been mostly digested and it starts to revert to clay. Then I till in as much compost as I can get my hands on.)

(Probably I wouldn't even have to do that if I was top-dressing with ENOUGH compost, spring and fall, but (1) I don't have much compost
(2) I always want to make more soil so I can have more raised beds
(3) I just LIKE turning the soil

In general, don't let raw manure touch plant stems and roots. It can get too hot, or too concentrated in soluble nitrogen.

If you have plenty of manure and pine straw, composting them TOGETHER before using them in the soil gives you the best possible solution. It conserves the most nitrogen and carbon for your soil micro-herd. (Raw manure can lose nitrogen to leaching if not composted together with plenty of browns). Now you can turn it under or top-dress at any time, and it is "pre-digested" by the compost organisms.

I never run my compost heap completely empty. The microbe and worm population always has a chance to migrate from the active and aged parts to the new part.

Also, I periodically re-inoculate my compost heap with soil from my healthiest beds, to encourage beneficial soil microorganisms to multiply in the heap. That way, they are present in large numbers when I turn compost into the soil, or just top-dress and let worms and rain do the work.

Charlotte, NC(Zone 7b)

A couple of caveats regarding fresh compost and manure:

1) Varmints love to eat fresh compost

2) Some dogs love to eat fresh manure (YUCK!)

(Carisa) Raleigh, NC(Zone 7b)

Yeah, I don't use fresh manure, never have. Way too much trouble and too smelly! I purchase a large load in the spring and they age it and mix it with plenty of browns, so it works great. I have just never used compost and don't have the patience or time to do my own, so I will just buy that from my local place, also. I think I might just do the aged manure mixture in the spring and the compost in the fall. Or either alternate them year to year, if I don't get a chance to do it in the fall. That should give my beds enough variety. I can't imagine (although I don't have much imagination when it comes to tilling, so keep that in mind) how to till or turn the soil in a perennial bed. Maybe you are talking about a veggie garden. That would make sense. My beds are way too packed for tilling, I would think. I would most certainly disturb roots that I shouldn't. I am going to start doing the worm tea thing, too, as an experiment in my beds. We'll see how that goes. This has been very helpful for me, thanks for all of the input.

Provo, UT(Zone 5a)

wish tapla would chip in on this.. he would have excellent advice on
this topic... HELLO??? heheehehe..

Everett, WA(Zone 8a)

>> I can't imagine ... how to till or turn the soil in a perennial bed.

Me neither! I've read two answers, but neither seem very satisfactory unless your perennial bed started out with very good, very rich soil. (None of my beds are that good yet.)

1. Top dress with compost spring, fall, and a few times in-between. Maintain mulch on top of that. Although mulch "should" be chunky enough to let rain and air through freely, it is also good if it breaks down and drips decomposing bits of humus continuously into the soil.

2. Every 3-5 years, MOVE all the plants out of one bed, into another bed (or maybe pots).
Once the bed is empty, go to town amending or replacing the soil. Then move plants back in (either the old ones, brand new ones, divisions from other beds, or move all the plants out of some other bed and dig dig dig that other bed!

(Carisa) Raleigh, NC(Zone 7b)

Uhhh, yeah, #2 is never ever happening, LOL. I would vote anyone that would to be gardener of the year!!! #1 is what I do now (sort of), and it is slowly improving things. I top dress, but with aged manure and fine mulch, mixed, but only in the Spring. I have never used compost, though, so I think I'm going to add that to my regimin. I think the variety will help. I have always used mulch in the past, but am planning to change the type this time, which is what generated this question originally. I was looking into different types and found that article! Thanks again for the great feedback.

Anne Arundel,, MD(Zone 7b)

#1 sounds realistic.
#2 no way. But in limited small bits, like when you divide certain perennials, then you can improve the soil as you plant back and fill in.

Enterprise, AL(Zone 8b)

I do what sallyg suggests, every time I move or add a plant I add compost. I could see doing my long beds in sections: removing all the plants ten or 15 feet at a time and improving the soil.

Everett, WA(Zone 8a)

True, #2 sounds like a method for people who have a full-time staff of assistants.

Even then, the soil had to start out really rich to keep them going for 3-5 years ... some of my "perennial beds" are hinting to me that they may "help" me do #2 by dieing off, to make the moving part easier for me.

Or here's another idea that is "yeah, right, sure, unnh-hunnh!" Most perennials only last so many years in any given climate. Plan ahead really far so that all the plants in one spot die or need to be divided around the same time!

I don't plan far enough ahead that I have enough room for the seedlings I start each year.

(Carisa) Raleigh, NC(Zone 7b)

I think that top dressing works better than adding to the hole as you plant. Plants need to be "trained", so to speak to grow in clay and when they have great soil just in the hole, they are hesitant to grow roots out into the tougher clay. I use to use the amend the hole method, but my plants didn't grow to full potential. Top dressing gives them the same enrichments, but they don't get used to perfect soil and just try to grow in their little bowl.

Charlotte, NC(Zone 7b)

There's another thread here somewhere that says one should not amend the soil when planting trees, shrubs or perennials. They all do better growing in native soil.

I won't be telling my fig or persimmon trees this. They are both growing in 25 gallon pots, and have broken through the bottom of their pots into the native soil and are doing well. LOL

Everett, WA(Zone 8a)

When breaking up clay, I amend the whole bed. But I think that as long as the soil structure is reasonably loose throughout, and moisture content does not change TOO much from one spot to another, roots can make the transition.

If most of a bed has reverted to soggy clay or hard clay, maybe it would be a mistake to amend just one hole to be loose and airy - roots might well stay there and never leave the hole.

Enterprise, AL(Zone 8b)

I think the article and the research for not amending the soil was strictly for trees and shrubs. I think annuals and small perennials do just fine with amended soil. Their roots don't have to travel all that far for the plants to succeed.I think they actually prefer amended soil.

Everett, WA(Zone 8a)

In my yard there is another reason to avoid an amended hole in pure clay. The hole is below grade, and the clay don't perk.

At the first rain, the hole fills with water and becomes amended, anaerobic mud slurry. Good only for mud wrestling.

Thumbnail by RickCorey_WA Thumbnail by RickCorey_WA Thumbnail by RickCorey_WA
(Carisa) Raleigh, NC(Zone 7b)

Yes, that happens at my house, too. It just does not drain! I read that article, too, then dismissed it. You can't NOT amend clay soil. Well, I guess, you could, if you wanted your list of plants to be about 5 deep. I, however, want every plant that I see! :) OK, you could probably get away with it with some types of trees or shrubs, but what are you going to do, make really good soil everywhere else except the place where that shrub is going? I do think that amending "by the hole", so to speak doesn't work, at least in my type of clay soil because of root laziness (we'll call it) and the bowl of water effect, like Rick said. Better to just fill the hole with the native soil after amending/mixing the entire bed before the first planting of that bed, then top dress from there. Any new holes get just the native soil added back in and a little extra top dressing, when needed.

Everett, WA(Zone 8a)

As you can see, I must have some mole ancestry (checking hastily to make sure this is not the GMO thread!)

I would say that, SURE you can dig a hole as far below grade as you want, in any kind of no-perk-clay, and fill it anything you want, as long as you are willing to cut a drainage trench from the lowest point of your hole, to some point that is even lower, and slope that trench DOWNhill at least slightly, all the way.

We who are "blessed" with good hard clay are "lucky". The tr5ench can be just a slit as wide as the blade on your mattock. The walls of our trenches are hard as concrete and may still be there centuries from for for future archeologists to ponder over. "Half Mole, Half Man?"

Charlotte, NC(Zone 7b)

"Half Mole, Half Man?"

Moleman! You're far too intelligent to be hiding in the dirt! LOL

Everett, WA(Zone 8a)

I just like digging and cultivating the soil more than I like cultivating plants!

While excavating the deepest part of my drainage ditch / walkway, between my tallest RB and another RB-To-Be, only the top half of my body was visible above driveway-level.

I imagine it was a disconcerting sight to anyone driving past my hovel.

Thumbnail by RickCorey_WA Thumbnail by RickCorey_WA
Charlotte, NC(Zone 7b)

just like digging and cultivating the soil more than I like cultivating plants

I'm the opposite. I love watching seedlings grow, then I like harvesting what grew, then I like to cook what grew, and lastly I like to eat what I grew.

Digging in and preparing the soil... not so much. LOL

Everett, WA(Zone 8a)

I also like seeing the seedlings put out rootlets on a paper towel, or emerging from the seed-start-mix. Those seem magical or miraculous.

If they survive all the way to bloom or harvest (an other miracle in my hands!), that's nice, too.

Sometimes I wish I could do the parts I like and let someone else do the rest, but I know I wouldn't be ab le to share. "MY" garden!!

I found the quote I was looking for:

The more help a man has in his garden,
the less it belongs to him.

- William M. Davies

But I would love to trade some digging for some hands-on help.

I'm pretty sure that someone looking at what I do would result in advice like:
"THAT'S why they all died!"
"Why are you doing THAT?!!?"
"You need more compost! More mulch! More weeding!"

Just last weekend I gave up on some beds that had been very overtaken by weeds. There may have been SOME perennials and re-seeders under all that, but I would never be able to find them. I pulled off the top few inches (the whole weedy root zone) and screened out the weeds and roots. Returned the soil.

Before putting the weeds and roots into my compost heap, I had an idea. I piled them where they can dry out and die, or compete with each other. That's also a spot where I will walk on them frequently. I'll chop it as needed, and turn it occasionally.

And I'll mock them and sneer at them when I do. "SO THERE, MR. WEED! Think you'll take over MY raised beds do you? HAH! Take that! And that!"

Enterprise, AL(Zone 8b)

Start you an all weed compost pile. Keep the weeds out of the good compost and put the weeds and other rejects in the separate pile. You can let the weed pile set a year if you need too. Turn it every now and then to make sure you have no new sprouts, then when it is finished and you are convinced there are no more seeds going to sprout add it to the garden or the regular compost pile. The weeds have a lot of nitrogen and will heat up fast helping to kill themselves. Of course frying them on the pavement will kill them too.

Everett, WA(Zone 8a)

Good idea, I should. I should. If I moved my main pile to a less visible spot to appease my annoying new neighbor, I could put a smaller weed-only pile where the main one used to be.

But I don 't really like he new neighbor enough to put my pile in a harder-to-reach spot.

First the walkway, then move the compost pile.
Before the walkway, move a pile of screened amended clay (near-soil).
Before moving the near-soil, prepare the bed it is destined for. That bed is full of rocks & roots!
Before any of that, start my spring seedlings ...
Before that, finish my spring weeding.

I've kind of fallen behind in my chores!

>> Of course frying them on the pavement will kill them too.

The PNW (or my spot near the coast) never gets hot enough to fry anything. The remaining soil will wash out of their roots where they are now, then I can spread them out to dry further.

The clay they are sitting on top of now is pretty hard - if any roots DO penetrate it, I'll probably cheer them on and buy them an ice cream cone for their efforts. Then kill them again.

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