yes it does matter as compost is the dissolution of components resulting in neutral ph for the most part.

Finished compost will have a pH near neutral, adding sulfur will do little to change that. As Jean said add it to the soil after a good soil test indicates how much might be needed to change the soil pH.

>Jean

Add it to the soil after a professional lab test tells you how much and how often to do so.<

+1

But curious why you need compost to be acidic?

Might want to grow more blueberries next year. Need to have some on hand. Can do a ph test by myself.

Ok is the soil where you intend to plant already at the pH you want? The location getting the right amount of sun? Plan on building something to keep the birds out?

No idea where you are but the native soil could be right where you need it.

Low pH good for potatoes too but I just toss my compost right on top of them, not saying you should just asking.

Soil is probably 7.5. Not a practical possibility. They don't sell acidified potting soil around here, so this is about it.

Used some of last year's acidified compost on Sweet potatoes. I don't know if that will work, but I certainly like their appearance.

I've found out that thiophilic bacteria operate at room temperature. I just figured I'd get a better mix and save a little time if I put it in from the get-go.

I have some going right now. First year. They only recently seem to be stabilized. It's almost like growing hydroponically.

I'll cross the bird bridge once I come to it. If I know what is good for me, I would keep them from fruiting next year in addition to this year.

Interesting. I'll keep an eye on this thread as someday I would also like to grow blueberries and some other perennials <grin>.

I do know if you don't cover them you won't get many so better to work on a plan before or simply build it into the design/layout.

A friend's parents build a cage over the beds using pvc pipe as the frame to hold the fencing with access so they could get in to harvest.

Good Luck.

I just did what Stark's suggested... amend with 1/3 the volume of the soil at planting with peat that had not had it's pH balanced. I rarely use peat, and I dislike using it at all, but this is one of the times I find it to be the proper product for the job. If you want to add compost instead of, or along with peat, just add the proper amount of sulfur to bring down the pH. Mine have been in the ground for 3 years and doing fine. Speaking of which, I got a specified fertilizer for them and need to apply that soon.

Some years ago I amended some of my soil (pH of 5.7 per MSU) with peat moss to lower the pH so I could grow blueberries and after a year that soils pH went to 7.2. Blueberries do grow wild around here but those plants just do not produce like the cultivated varieties.

kokopellifivea, have a good soil test done, not with something from the garden center or with litmus paper. If your states Cooperative Extension Service does soil testing they will tell you how much sulfur you need to add to the soil to get the soils pH where it needs to be to grow blueberries. Commercial labs may not do that.

My wife says she uses a pelletized sulphir product on our blueberries because the powder is messy. Add water. The plants are huge and more produtive than we can consume. She also has pinestraw under them.

The original poster seems to be asking why he can't just acidify his compost ahead of time with the sulfur and then amend the soil with the compost rather than adding the sulfur to the soil to acidify the soil. I think there are several reasons this won't be effective. The reason that elemental sulfur acidifies soil is that bacteria in the soil convert it to sulfuric acid. We may assume that it does so in low concentrations diffused throughout the soil, and we know that it takes time for this reaction to take place and acidify the soil. It's important to know the proper amount of sulfur to apply to the soil: too little would not be effective, and too much would probably be detrimental. That's why a soil test with sulfur application recommendation is so crucial.

If you were to add sulfur directly to the compost, I can guess that at least some of the same bacteria would be present in the compost and would produce some sulfuric acid in the compost. But then what? You've got to store the compost for some period of time; meanwhile, the organic matter content of the compost is much higher than the organic matter content of soil, so it has an increased capacity to buffer pH, therefore presumably reducing the acidity over time.

Sulfuric acid is also highly soluble in water and is probably prone to mobilization in the compost material as moisture content in it changes, or it is exposed to rain, etc. Now you've got to know how much compost to add to the soil to achieve the desired alteration in soil pH: how are you going to determine that? How are you going to know how fast the pH of the soil will be changed and how long the alteration will last? Again, the sulfuric acid is soluble in water, so every time it rains or you water or irrigate, the concentration will change.

I think we use sulfur to modify soil pH directly because it causes the sulfuric acid to be formed directly in the soil in a distributed fashion at a fairly predictable rate and concentration. Obviously it isn't precise, but I think attempting to produce acidic compost by using sulfur is a lot more uncertain and imprecise and the subsequent effect on the soil may be wholly unpredictable.

To simply answer your first post, it would be better to add
sulfur to warm compost while bacteria is more active. With cold soil or compost, the bacteria is
not as active and thus sulfur is not being converted to sulfuric acid as
quickly. Since the process takes weeks
to several months, you will save yourself some time by adding it to the
compost...and when it is warm. Since it
is a slow process, this is a proactive way to reduce pH.

With regards to the spot where you plan on planting the
blueberries, I agree with others' comments on the soil test as current pH alone
isn't the only factor in determining how much sulfur to add to the soil. Some sites recommend rates based off of the
soil structure (sand, silt loam, clay) but rates of free calcium carbonate in
the soil are also part of the equation which will be (should be) included in
the calculation by your local extension after you get a soil test to determine
if additional sulfur is needed beyond the normal application for the size and
soil structure. Here are a few links you
may be interested in:

http://cesanluisobispo.ucanr.edu/files/152040.pdf

https://ohioline.osu.edu/factsheet/agf-507

http://www.clemson.edu/extension/hgic/plants/other/soils/hgic1650.html

http://msue.anr.msu.edu/uploads/files/Lowering_Soil_pH_with_Sulfur.pdf

https://garden.org/nga/calculators/index.php?type=sulfur

Though finished compost alone tends to have a neutral pH
this is usually what is reported from conventional compost piles…not those with
elemental sulfur added. Adding sulfur
will effectively decrease the pH... it is one of the few amendments that you
can add to achieve a long term reduction in pH.
Plant based amendments that naturally have a lower pH (such as oak
leaves) seem to have a short term effect as they return to a neutral pH (similar
to compost…since they are composting the ground, as opposed to your compost bin). Sure, compounds in the compost will fight
back and may work to bring the soil back to a neutral pH, but not completely
back to neutral as it would with the absence of the added sulfur. How much exactly is very hard to say as it
all depends on the ratios involved. It's
not quite fair to say it will be a futile effort.

Further, what's the harm if you overdue the compost and
bring it down to a pH of 3? If you're
just setting it aside to amend to your soil before planting blueberries, just
add less, wait a few weeks and retest your soil. If you need to reduce the site further,
you'll have readily available compost to add.

It's usually recommended to work on your soil a year in
advance of planting blueberry plants so you have time to continue to add
compost, test and readjust. Adding more
compost is always good for blueberry plants anyway...high amounts of organic
matter is good for the roots and has a lot of additional benefits. I’ve seen many people report that their
blueberry plants do very well with less than ideal pH but high amounts of
organic matter (and proper drainage) than if the pH was ideal but planted in
otherwise poor soil.

Lastly, remember that the soil is ever changing. If it wasn't where you wanted it from the
beginning, it will likely take years to get to a steadier state. It's sort of like exercise, if you don't keep
on monitoring your progress and working at it, your efforts can quickly
fade. I would recommend testing your pH
twice a year at the start (I would just use a garden center test after the
initial extension test to save a little money) and maybe reduce to testing
annually but only after you see that your pH has remained somewhat steady.

If your current soil has a pH of 7.5, I would not recommend planting blueberries in the ground. You will not be able to get your soil to a sufficiently low pH and keep it there to keep the blueberries happy. Any significant pH adjustments (more than a full point on the scale) will be very temporary at best. The vast majority of soils have a buffering capacity that will resist any semi-permanent pH change and will resort back to the original pH or close to it in very little time....often just after a single growing season or a year or so.

Right. That's why I'm making acidic compost for container growing. They don't sell acidic potting soil around here.

Compost - whatever its pH - is not a suitable ingredient for a container planting mix. It is excessively moisture retentive and will continue to break down, compressing, collapsing and becoming finer and finer particles. This will impede good drainage even more.

It is pretty easy to make an acidic potting soil mix. Just start with pine bark fines (about 50% of total volume), add another 25% of untreated peat moss (no pH neutralizer added) and the remaining 25% a combination of perlite, pumice, granite grit, calcined clay or any other stable drainage enhancement. Do not add lime to adjust pH.

Both the bark and the peat especially are quite acidic and should result in a pH that is suitable to growing the blueberries. No need to add sulfur although if your soil is so alkaline, so may your tap water be also. I would test that then add table vinegar to any irrigation water to acidify if necessary.

Your formula is pretty close to what I made last year. Diatomaceous earth instead of calcined clay, plus the acidified compost. I live in a dry climate, use porous grow bags, so, no problems with excessive moisture retention so far.

Surprisingly, acidifying the water hasn't been inconvenient at all. I use almost 100% sulfuric acid mixed to about a 3.5% solution. ( Six capfuls of "Liquid Fire" pipe cleaner at Ace Hardware mixed in a 1.75 L liquor bottle taking all precautions) That is equivalent to about a 7% vinegar solution in terms of strength. Four capfuls of that to a five gallon bucket is plenty. Two capfuls if that takes my tapwater to an even pH of 6, to put things in perspective.

The irrigation water influences the pH a lot; no way would this work with acid soil only.

I use commercial fertilizer for N for my compost. So I compromised by using Ammonium sulfate in addition to my usual urea. I will add additional S later when it goes down to 120 F or so.

If you wanna make acidic soil, use vinegar after the process complete. Vinegar is acid buffer, which mean, easier for it to turn back to it's state when the basic molecule gone. If you use acid solution that's not supposed to use as buffer, they will react with basic to become salt that reduce soil quality, and lost their ability to be buffer.

Where in the world are you? I cannot imagine any place, in the USA, that does not have a garden store that does not sell acidic potting soil.

Rural southwest USA. Not Rhododendron country.