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mulch: aged sawdust, ashes, coffee grounds
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Posted by
joannaqcw NY 4/5 (
My Page) on
Thu, May 3, 12 at 9:33
| I'm interested in doing more with organic mulch. We have periodic access to grass clippings, which I know how to handle, and steady access to sawdust (we've been aging ours 12 months before applying it; it's mixed hardwood/softwood), coffee grounds (both fresh and somewhat decomposed), and wood ashes (mixed hardwoods, from our wood boiler).
I know the sawdust and coffee grounds are apt to be somewhat acidic and the ash is fairly alkaline. I don't know in what ratio to mix the three to put around plants in my garden, which I believe to have somewhat acidic soil because of the weeds we have (horse nettles, volunteer strawberries..) and the vegetables which typically thrive or fail to thrive in it (tho our blueberries haven't taken off in site of pine needle mulch, so I am guessing it is not hugely acidic).
Any advice/stories would be greatly appreciated. |
Follow-Up Postings:
RE: mulch: aged sawdust, ashes, coffee grounds
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| I would go very easy on the ashes, especially if you are putting this stuff directly around plants. I also have ashes from my woodstove which I look for ways to reuse, but have not heard of or tried what you suggest. Coffee grounds are *very* weakly acid, most all of the acid ends up in your coffee cup. The sawdust is probably fairly neutral also since it was aged for a year (presumably in moist conditions. I'm thinking a quart or two per cubic yard of organic material. You might want to get a soil test and find out what your pH *really* is. |
RE: mulch: aged sawdust, ashes, coffee grounds
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- Posted by jolj 7b/8a-S.C.USA (My Page) on
Thu, May 3, 12 at 22:04
I know people who used green/fresh sawdust on top of the ground.It was mostly hard wood & did not hurt the soil or harm the plant.
So your cured sawdust should be fine. |
RE: mulch: aged sawdust, ashes, coffee grounds
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The pH of coffee grounds I have seen reported as anywhere from 3.0 to 6.9, but the one I would put most faith in is the one Starbucks had done which put the pH at 6.2. Every soil scientist I have heard talk about adding wood ash to soils says to have that soil tested for pH before adding tht ash, and only add the ash of that pH test indicates you should.
"Aging" sawdust will do nothing to change the C:N ratio if no Nitrogen source is added so it makes little difference if the sawdust is used fresh, green, new, or aged. The C:N ratio of fresh sawdust will be about 500:1 and the C:N ratio of aged sawdust will be about 500:1.
Although Pine needles test at a pH of about 3.7, just as Oak leaves do, as they are digested by the soil bacteria the pH evidently changes, toward neutral. Pines grow where the soil is acidic, not because the needles they drop changes the soil pH. Over the years as I have added organic matter to my soil with an initial pH of 5.7 that has changed to todays 7.2 without adding anything else.
Contact your local office of the Cornell Cooperative Extension Service about having a good, reliable soil test done so you have some idea what might need to be done. |
Here is a link that might be useful: Cornell CES
RE: mulch: aged sawdust, ashes, coffee grounds
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| kimmsr, I would dispute the statement that pines grow where it is acidic. Pines also grow in alkaline soil. There are many native pines in my area that are growing in a limestone based soil. |
RE: mulch: aged sawdust, ashes, coffee grounds
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| If sawdust is aged outdoors in a pile that gets rained on, it starts to decompose. Although slow, that process would begine to change the C:N ratio in the direction of of finished compost, correct? |
RE: mulch: aged sawdust, ashes, coffee grounds
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| With the exception of the wood ashes, the remaining items can be used as a mulch at will. A mulch - or topdressing - has a minimal impact on soil pH regardless of what the pH of the mulching ingredient is. There is a some minor leching involved but the alteration of soil pH is insignificant and occurs only at the soil surface.....no penetrating or longterm effect on the deeper soil. The big concern with these (UGC's, sawdust) as mulch ingredients is that they crust over when dry and become hydrophobic and do not allow water penetration. There is a far different effect with wood ashes. Because they are virtually disolvable in water, they make an ineffective type of mulch - they disappear with rain or irrigation - and the leaching effect is far more pronounced. And they are extremely alkaline and can easily adversely affect the growth of plants that prefer more acidic or neutral soil conditions. Use in moderation as a compost ingredient or apply very lightly to those plants that prefer more alkaline conditions or demand that boost of K. |
RE: mulch: aged sawdust, ashes, coffee grounds
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tishtoshnm, there are some evergreens that will grow, and prefer soils that are more neutral and many people think all evergreens are pines. There are also some few pines that will grow in slightly alkaline soils. Are those trees you see growing true pines or are they Junipers, Spruces, or Yews?
toxcrusadr, I've not seen anything, yet, to indicate that the C:N ratio of sawdust changes as it ages. Stuff that once was sawdust, that has been digested, does have a different C:N ratio but I do not have access to anything that says what that is. |
RE: mulch: aged sawdust, ashes, coffee grounds
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| In our area, there are many pinon pines and I think Ponderosas (but I am not entirely sure, they are not on my property). I am certain they are a pine. I do have native juniper on my property those are more like large shrubs than trees to this girl born in Oregon but that is another story. As far as non-natives, we have Austrian and mugo pines that are also growing great in our soil with no supplementation or adjustment to the pH. I am not familiar with yews so I would not know one if I saw it, but I am quite familiar with pines. |
RE: mulch: aged sawdust, ashes, coffee grounds
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| Italian stone pine grows in alkaline soil as well, and it's the only one I care to mess with, it's been cultivated so long it's not really a "natural" native of anywhere...there are just a few alkaline tolerant pines, and they have adapted special features in a few very tough climates, that are not found in and not representative of the rest of the genus. Junipers, spruces and yews ho ho, junipers, spruces and yews, ha ha...true and funny if you can make a jig of it... |
RE: mulch: aged sawdust, ashes, coffee grounds
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..
Mulch something on top of the used coffee grounds and sawdust to negate the crusting effect. I like grass clippings. The little bit of leaf mulch I tried once worked too. Worms dig the coffee grounds. With grass clippings on top of the coffee grounds, I've found many close to the surface in my hot dry climate and hard soil. Let the worms work that stuff into the soil.
.. |
RE: mulch: aged sawdust, ashes, coffee grounds
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| For all I know, man has messed with all the alkaline pines... austrian pine, cultivated by the arabs, pinion pine, cultivated by the indians, stone pine, cultivated by the mediterraneans, ponderosa...well, there was this western back in the sixties, and I believe the cowboys were cultivating them by then. |
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