Making soil more acidic

cymraes(8)May 4, 2009

I bought some blueberry plants and the instructions say to add lots of peat moss to increase the acidity. I prefer not to use peat moss due to the environmental effect. Is there another way to increse the acidity? What I have available is horse manure mixed with straw (varying from 2 to 7 months aged), several old dead pine trees and old rotting hay. I've read that pine needles increase acidity, but I'm not sure if the dead needles do the same? Help?

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greenwood85(6b)

Soil sulphur is the only thing I've found.

    Bookmark   May 4, 2009 at 3:53PM
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idaho_gardener

There are informed people, like Eliot Coleman, that feel that there is no need to worry about the effects of harvesting peat moss. I'll use it on occasion, but for soil pH, I'll use agricultural sulfur, humic/fulvic acid, pine and spruce mulch, and compost.

Good luck.

    Bookmark   May 4, 2009 at 8:18PM
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gardengal48

How much more acidifying is necessary will depend on the current pH of your soil, but blueberries don't require highly acidic soil - they thrive in my area in a slight to moderately acidic soil (6.5-6.0). What they do prefer is a highly organic, fertile soil that is moisture retentive. Peat moss is typically recommended for blueberries because it combines the organic, moisture retentive characteristics along with its acidic qualities but other amendments can work equally as well. I'd add the manure to the planting area and perhaps some of the rotting hay, then any agricultural sulfur as might be determined necessary. Amending or mulching with cottonseed hulls or meal will help also - it is a natural acidifier.

Pine trees, pine straw mulch or other conifer debris really does not offer any significant acidifying qualities to the soil - that's a gardening myth that has been disproven scientifically.

    Bookmark   May 4, 2009 at 8:54PM
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rj_hythloday(8A VA)

Pine bark fines are the number one ingredient in Al's mixes (container recipes) and dolomitic lime is added for ph adjustment. Woulnd't pine bark fines w/ out the lime work? I'm not talking amendment, but digging a hole and filling it w/ fines and maybe some peat and perlite or vermiculite or expanded shale. I want to grow rasberries in containers to transplant later when I own a house, I don't know if it will work yet, but this is what I have in mind.

Here is a link that might be useful: Container Soils - Water Movement and Retention - A Discussion About Soils

    Bookmark   May 5, 2009 at 8:15AM
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Kimmsr(4a/5b-MI)

Since it is known that adding Oak leaves (pH of 3.7) and pine needles (pH of 3.5) to a soil will not significantly change that soils pH why would adding peat moss (pH of 4.6) do what they will not? When I added some peat moss (a 3.8 bale to a planting bed 4 x 4 and worked in to an 8 inch depth) the soil pH in that bed went from 5.7 to 7.2.

    Bookmark   May 5, 2009 at 8:19AM
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dan_staley(5b/SS 2b AHS 6-7)

the soil pH in that bed went from 5.7 to 7.2

Peat moss is acidic. The pH should have dropped, so something else happened.

Nonetheless, sulfur is how to acidify soil in a lasting manner. Vinegar works for about a week but can damage roots. Pine needles and lvs do slightly but not permanent (but a good mulch). Having good humus and OM in the soil is a key.

The reason why blueberries prefer acid soil is that those pH ranges make certain minerals more available to the plant. Ensure that the soil amendments and fert regime provide what the plant needs, as they are far easier to care for if happy.

Dan

    Bookmark   May 5, 2009 at 9:42AM
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gargwarb

Since it is known that adding Oak leaves (pH of 3.7) and pine needles (pH of 3.5) to a soil will not significantly change that soils pH why would adding peat moss (pH of 4.6) do what they will not? When I added some peat moss (a 3.8 bale to a planting bed 4 x 4 and worked in to an 8 inch depth) the soil pH in that bed went from 5.7 to 7.2.

A special thanks to our ambassador from the plant WooooOOOOOOOooooo....
Instead of dusting off that wacky old anecdote, think about it. You can add peat to decrease the pH, depending on the volume you add.

Let's say you have a pile of alkaline soil next to a pile of peat moss, which is acidic.
Now Take one cubic yard of soil and add to it one cubic foot of peat. Will the final pH be close to that of the alkaline soil or the acidic peat? Why, closer to the alkaline soil, of course because the final blend is mostly alkaline soil.
Now take one cubic foot of alkaline soil and add one cubic yard of peat. Will the pH be closer to that of the alkaline soil or the acidic peat? It will be closer to that of the peat because the final blend is mostly acidic peat.
Now do a 50/50 blend of soil to peat. Will the final pH be closer to that of the alkaline soil or the acidic peat? Well, by golly, I'm going to go out on a limb and say that the pH will be somewhere in between. Your final product will be both more alkaline than the peat to begin with and more acidic than the soil to begin with. As you play with the percentages, you will be adjusting the pH (and other chemistry) right along with the physical properties.
The finer the soil, the more peat it takes but adding peat acidifies the final product in pots and on the ground.

I don't know what you did in your isolated anecdote that you keep throwing out there every time this comes up but trust me, you did not change the fundamental laws of nature.

    Bookmark   May 5, 2009 at 9:44AM
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bug_girl(17)

I use aluminum sulfate and I use acid type of plant foods on all plants because I have super alkaline water and soil. Each time I put my meter into the ground the soil is always super alkaline. Just use these products sparingly or you may burn the plants. If you want to be more organic, coffee grounds mixed in will increase the acid level as will things like pine needles. If you compost that is helpful to break down the coffee and pine needles first. I don't like using peat. It is expensive and it seems to break down too fast, but it is a option. One bag costs like 20 dollars.

    Bookmark   May 6, 2009 at 10:53AM
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rj_hythloday(8A VA)

The problem I see w/ using peat, beyond the renewable thing. Is that peat breaks down, how long is the ammended soil going to remain acidic? Is it going to be necessary to keep adding peat every year? Wouldn't something like pine bark fines last longer and keep the ph where it's needed longer?

    Bookmark   May 6, 2009 at 11:04AM
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Kimmsr(4a/5b-MI)

Dr. Abigail Maynard, a pHD in soil science, did the research at the New Haven Agricultural Research Station, New Havben, Connecticut and over several years added large volumes of Oak leaves and pine needles to soils adn tested the soils pH and found there was no significant change in the soils pH, as reported in Organic Gardening magazine a while back. I have seen no research that has definitively shown that adding any organic matter to soil will significantly change a soils pH and my experience indicates that adding peat moss will not no matter how many people repeat the old myth that it will.
A short time ago the horticulturist, Kip, on Victory Garden stated he liked adding peat moss to soil because it lasts so long in the soil, ie, the soil bacteria will not digest it.

    Bookmark   May 6, 2009 at 1:12PM
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gargwarb

If you make a potting mix that is 50/50 peat to alkaline sand you may still have to include some lime. Why? Because if you don't, the mix may be too acidic. (But that can change from one to the next depending on the initial chemical properties of both components and the intended plant material)
If you buy a backfill mix for your acid loving plants to be blended with on site soil, usually it's mostly peat. Why? Because it's acidic.
If you mix a very strongly acidic material into a soil, it will have an effect on the pH of the final product.
However, if you mix in a small amount, the effect will be small and maybe even immeasurable. It does depend on a whole slew of factors including but not limited to amount used, buffering capacity of the soil, lime content of the soil and the pH values you started with in each material.
That being said, soil sulfur is the best all around way to adjust soil pH downward. Iron sulfate is 2nd, aluminum sulfate is 3rd.
My point is not that peat is the best way to do it. My point is that when it comes to peat affecting soil pH, it's not a simple matter of yes it will or not it won't. To say that peat will never lower the pH of any soil, regardless of all the possible variables to consider, is delusional.

    Bookmark   May 7, 2009 at 9:00AM
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greengardener07

Contrary to popular belief, peat moss is very renewable. I would not worry about running out of it. Many publications have verified this.

    Bookmark   May 13, 2009 at 1:02PM
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dirtydan(8-9 Lancaster, CA)

I think that the difference in buffering capacity of the soils in question is the reason that people see different results and disagree on this topic.

Here is an example of how buffering capacity of the medium will affect pH changes.

Assume we have two different 100 gallon tanks of water.

Tank number one is pure distilled water. To this tank we add a few drops of sodium hydroxide to raise the pH to 8.5.

Tank number two is water drawn from a well with very high levels of minerals primarily consisting of calcium (Ca2+), and magnesium (Mg2+) metal cations ("hard water"). This water measures a pH of 8.5.

Now we have two tanks of water that both measure pH at exactly 8.5. But both tanks are not created equal! "Think; two different gardens, both with pH 8.5 soil"

We want to lower the pH to neutral so we will need to add an acid to both tanks.

Tank number one will only need a few drops of hydochloric acid to lower the pH to neutral, while tank number two may require 100x more acid to become neutral.

The reason for this difference is the buffering capacity of tank number two due to the high levels of calcium and magnesium metal cations.

This has been my hands on experience from hydroponic gardening and I believe that the same chemistry applies to acidic soil amendments such as peat moss.

Therefore, depending on the specific soil buffering capacity, gardener number one may require only a small amount of peatmoss (by volume) to change the pH of his soil from 8.5 to neutral, while gardener number two may require vastly larger amounts.

Here is a link that might be useful: My soil test, oh happy days..... not

    Bookmark   May 15, 2009 at 3:45PM
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idaho_gardener

Regarding soil pH experiments in New Haven. New Haven gets about 50" of rain per year. SouthWest Connecticut is a temperate rainforest environment. I come from there (Ridgefield, Ct.)

Since pH is a function of water, that experiment is not applicable to much of the rest of the country.

    Bookmark   May 15, 2009 at 3:54PM
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Lloyd

"A special thanks to our ambassador from the plant WooooOOOOOOOooooo...."

snort, chortle, guffaw (wipes tears from eyes)....

Might PM from different sources also have a different Ph thus affecting even similar soils differently? Perchance not all soils are that similar leading to vastly different results? Maybe some things aren't quite as black and white as some people make them out to be?

Just asking.

Lloyd

    Bookmark   May 15, 2009 at 3:59PM
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Xtal(z8b Temple. TX)

I'm so glad to see these postings still accessible. One day I'll focus on amending my alkaline soil for a couple of blueberries. So, I thank all you guys for your input.

Xtal

    Bookmark   May 24, 2013 at 12:05PM
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