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Pine Needles?

Posted by liisa_rwc 10b Bay Area CA (My Page) on
Wed, Nov 26, 08 at 20:36

Hello,

I'm new to composting and want to know... what's the risk of using mostly (75 to 80%) pine needles as the "brown" for my compost bin? Will the finished compost be high in acid?

Thanks!
Liisa


Follow-Up Postings:

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RE: Pine Needles?

Not high in acid but it may take a while for them to break down. I used to have about 30-40% pine needles (now I just rake them in beds as part of the mulch) and they certainly helped keep the pile aerated. I used the compost after about 2 months of cooking in those days and the needles became...well...noodles for the most part. They did add bulk to the finished product.

tj


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RE: Pine Needles?

Thanks tj :-)

Liisa


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RE: Pine Needles?

Many people that should know better mislead others by stating that a soil is "high in acid" when the real problem with that soil is a lack of oxygen molecules, an acidic soil just has more free hydrogen ions than a soil closer to neutral, so no your compost composed mostly of pine needles will not be "high in acid". There is also an old, and persistant, myth that pine needles make soil, or maybe compost, acidic but they will not, because the wee buggers that digest the organic matter that we compost work to make that nearly neutral.


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RE: Pine Needles?

"an old, and persistant, myth that pine needles make soil, or maybe compost, acidic but they will not"

Another myth busted... :-)

Thanks.. I was one to believe that myth to be true.
Now I know better.

Liisa


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RE: Pine Needles?

80% pine needles as your source of browns isn't ideal. It will work eventually but there are much better browns available and 80% of anything as a component should be avoided if possible. Diversity is the key to great compost. ;)

As tj said, pine needles are VERY slow to decompose - a walk in the piney woods shows that - so the carbon activity in your pile will lag behind the nitrogen activity. Got any leaves or cardboard or even shredded newspaper you can throw in to better balance the ingredients?

And a bit of a disclaimer or clarification if I may about the "myth busting" - we are talking about 2 different things.

While it is true that all compost reverts to a basically neutral condition as it finishes - even compost with pine needles - while the process of decomposition is taking place pine needles are acidic as opposed to an alkaline ingredient.

So pine needles are acidic and incorporating large amounts of them into the compost pile or into the soil can temporarily change the ph of the compost/soil. Finished compost containing decomposed pine needles is basically neutral.

Dave


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RE: Pine Needles?

Well then I have a lot to learn... As far as other leaves.. not many and not in my yard. I get some blowing in from other trees that I don't have access to. The pine needles are next door in my sisters yard so they are very accessible. I will start holding on to cardboard boxes.. I don't get the newspaper so I will keep my eyes open for them at work... I'm already taking UCG from there so I'm sure I can find a newspaper or two laying around.

Thanks again.
Liisa


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RE: Pine Needles?

Among the many studies that have shown that pine needles do not significantly change a soils pH is one done by Dr. Abigail Maynhard at the University of Connecticut Agricultural Research Station at New Haven, Connecticut where she found that adding large quantities of pine needles or Oak leaves did not make a significant change in soil pH in the test plots. There is not any research that I have found that shows the opposite, just annecdotal myth promoting statements saying I was told " ".


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RE: Pine Needles?

  • Posted by pt03 3 Southern Manitoba (My Page) on
    Fri, Nov 28, 08 at 13:00

Same poster....

Nov 28, pine needle thread

"...just annecdotal (sic) myth promoting statements saying I was told"

Nov 26, horse manure thread

"I have been told by those in the know that there are probably 10 people that get sick for everyone reported..."


CDC website...

"CDC estimates that 38 cases of salmonellosis actually occur for every case that is actually diagnosed and reported to public health authorities"

Took me longer to type this than to find it.

Lloyd


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RE: Pine Needles?

Actually Dr. Maynard's (note spelling) study was done with the effect of leaf mold fine sandy loam. Per her report, she "used unscreened leaf compost was applied at the rate of 50 T/A (one inch on the surface), 25 T/A and 10 T/A. Compost was rototilled into the soil to a depth of six inches. Compost was produced in a passive pile turned four or five times yearly for two years. In all three years of compost applications, virtually no difference was found in soil nutrients between the compost treatments and the control. However, differences were found in organic matter percentage and pH between the treatments in all three years."

The issue under discussion here is the use of uncomposted pine needles - or "fresh" pine needles. My point above was that while composted pine needles will be essentially have a neutral pH, the application of UN-composted pine needles will TEMPORARILY alter the pH of the soil or compost to which they are applied. It will be, for however much time it takes for the pine needles to decompose (which varies according to climate), have an easily tested, acidic pH. The same is true of leaf mold.

One can easily test this for themselves using a pH meter and many have done so, myself included. Pine needles have a pH of 5.8-6.2 - clearly acidic. So while the change won't be profound, it will be on the acidic side of the scale.

Dave


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RE: Pine Needles?

Dave, many years ago I did a pH test on pine needles,as well as other deciduous tree leaves, and found the pH of pine needles to be in the same range as other tree leaves, between 3.2 and 3.8 pH. This was using a good laboratory pH meter not a very inexpensive home model which are known to be not very reliable. My test was done by crushing the needles into some distilled water and allowing that to steep for 24 hours. How did you do your test?


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RE: Pine Needles?

"One can easily test this for themselves using a pH meter and many have done so, myself included. Pine needles have a pH of 5.8-6.2 - clearly acidic. So while the change won't be profound, it will be on the acidic side of the scale. "

Do you people know what the ph numbers mean?
The higher the number the less acidic something is.
5.8--6.2 is perfect acidity for most vegetables. I get similar numbers on the potting soil bags I buy from the store. So 5.8 is not acidic , moreover rainwater is given to have ph 5. Finally , vegetables do not like too alkaline soil 5.8--6.2 is the perfect range


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RE: Pine Needles?

Yes we do know, but I'm not totally sure you do. 5.8 is indeed acidic. Maybe not overly acidic for vegetables, but certainly acidic. :-D

The thing about rainwater is that it's basically distilled water and has virtually no buffering capacity. It may be acidic but can be changed quite easily (almost by looking at it just right). Whereas compost leachate, soil pore water, etc. has much more of a buffering capacity. Academic I suppose.

The original question was whether pine needles would make acidic compost, and I agree the answer is generally no.


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RE: Pine Needles?

The pH scale is an arbitrary development to indicate something and ranges from 0 to 14 with 7, the midpoint, representing neutral. Numbers less then 7 indicate a soil that is acidic while numbers above 7 indicate an alkaline soil. Each progression on the scale, logrithmic, means a 10 degree change, so a soil with a ph of 6.0 is ten times more acidic then a soil with a pH of 7.0.
Since most all nutrients plants need are most readily avialable when the soils pH is in the 6.0 to 6.8 pH range most all manufacturers of potting soils will do what is necessary to make sure these materials are in that range.


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RE: Pine Needles?

To kimm's original points made several years ago ... see link below from the University of Wisconsin Cooperative Extension, Nov. 2010.

kimm - is that your pH research they report?

Here is a link that might be useful: Pine Needles Cause Acid Soil - Fact or Fiction


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RE: Pine Needles?

We have 2 big pine trees. After trying to compost the needles with the rest of my compost, I realized it takes at least 3 years to break those needles down, so I've started a special bin to compost them. Now, they can take their sweet time and I finally have a way to break down our prodigious supply.


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RE: Pine Needles?

That article does reference the work that Dr. Abigail Mayhard did at the UCONN Ag Research Station iin New Have, Conn. The pH of various leaves is research I have done myself although that was instigated because I saw an artilce about the pH of various tree leaves and pine needles. That is a good article TXEB, hopefully it will help dispel some of the myths that persist.


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