^ what about a fish emulsion type fertilizer, with citric acid added to reduce the pH?

organic_wonderful,

You can use fish emulsion fertilizer along with liquid kelp.

If you want to lower your pH, just use elemental sulfur.

I think I read that someone (Al?) said that sulphur is bad to use on potted plants since it can form toxic compounds like sulphur dioxide. Is this not the case? Shouldn't I just use vinegar or citric acid?

organic_wonderful,

You can use any of the three, I was just giving you another option if needed.

Too much of anything can be toxic to plants. I use elemental sulfur because I don't have to apply it every time I water and it is a buffer to keep the pH stable.

OW - I think you were probably remembering a comment about hypoxic conditions (soggy soil) producing noxious gasses like excess CO2, methane, and sulfurous compounds like SO2, but that happens regardless of whether or not you add additional S to the soil.

If I was going to try to manage pH, I would probably do it by using an acid like vinegar or citric acid instead of S. The reason say that is because even though there is little danger of a S toxicity, you have no control with elemental S, and its near complete insolubility makes it much less effective than an acid source.

Al

tapla,

Can you explain yourself on how you have no control with elemental sulfur?

How much elemental S would you add to 3 gallons of soil to lower the pH one full number (say from 6.0 to 5.0), and what size particles must you use to achieve your goal? What effect will it have on the pH of the soil solution, which is the most important consideration? There's no way of knowing.

Using a pH test kit very occasionally and adding vinegar or another acid like citric acid to the irrigation water, it's fairly easy to consistently hit a soil solution pH within a range of 1-2 tenths of a whole number.

Al

^ Are you against using sulphur on the soil in the ground, tapla?

Tapla, would you recommend using diluted urine to fertilize blueberries, since it obviously contains urea?

I don't have a lot of preset prejudices, so I'm not for or against using elemental S in the ground, but I think I would depend on soil test results indicating a S deficiency or that it would be the best way to lower soil pH.

I'm sorry, but I can't see the point is using urine for plants. It's incomplete as a fertilizer, so you're going to need to fertilize anyway, the end result being that you have no idea what or how much N you supplied. It just makes more sense to me to use a fertilizer you KNOW is supplying nutrients in a favorable ratio, instead of duplicating SOME nutrients unnecessarily. I look at urine applications as raising the EC/TDS of soils without reason and for no gain. I'm all about results & efficacy - what works best, & I can't see urine as a + in either dept.

Al

Sulfur has to be acted on by soil micro-organisms in order to acidify the soil, and this process is fairly slow - it can take months even in soils with a lot of organic matter. Microbe populations/activity in containers tends to be erratic, so sulfur isn't a dependable pH adjuster for that application.

That said, sulfur has worked really well for me in the ground... it should be worked in well and incorporated regularly, perhaps supplemented with molasses or sugar to increase microbe activity.

Unless costs have become extremely prohibitive or you're very committed to permaculture and sustainably growing crops, I have to agree that urine probably isn't a great idea. Urine will increase pH before it lowers it, and won't lower it by much... it will do so in the same that any nitrogen fertilizer would. Ammonia is the first microbial decomposition product - it's quite basic. Ammonia is further decomposed into nitrates and nitrites in a process that lowers pH. The conversion is fast, usually taking place in days or less.

Before decomposition, urine actually has very variable pH, depending mostly on how much protein you eat (urea is a protein catabolism end product). The amounts of various nutrients is also highly variable. More importantly to me are the high levels of salts and other synthetic chemicals in urine (prescription drugs, all kinds of exogenous organic compounds from environmental exposure, potentially heavy metals).

If you're going to use urine, you should be sure to water heavily from time to time to flush out accumulated salts. If you're intent on using it, I think the best way is to simply add it to your compost and use it for your in ground plants. Here it has a chance to be fully metabolized by microorganisms, and composting is always an imprecise process anyways.

Citric acid can be bought at Chinese and Asian grocery stores. It may be labeled as lemon salt, sour salt, or in Indian grocery stores - "nimboo phool". It's extremely cheap and good quality.

Also, you can use Wolfram Alpha to quickly calculate the pH of any solution of acetic acid (vinegar). Citric acid would require a way of measuring mass if you wanted precise pH calculations.

Regular grocery store vinegar is 5% acetic acid. You can use the input "5% acetic acid" to get the pH of the solution about halfway down the results page. Calculate the new percentage based on the volumes of your dilution, and you can get precise pH. For example, 1 tbsp of vinegar per gallon would be 0.019% acetic acid, giving you a solution pH of 3.7

Here is a link that might be useful: Wolfram Alpha

..... except that in almost all cases, growers will be adding the acid to tap water, the buffering capacity of which will vary significantly. The buffering capacity of a solution is a very important consideration in calculating its end pH after adding an acid or base.

Al

Would I be right in saying that peat moss alone would be much better to add to the soil to raise the pH? I have pH 7 soil on my allotment that I want to raise to about 6-6.5, so I was thinking it would be a better alternative, since I haven't got time to wait ages for the sulphur to be broken down by the soil biology. Any thoughts?

In response to tapla's comment above this post, would distilled water be much better for pH tests?

^ sorry, I meant 'would distilled water be much better for soil pH tests if tap water buffers the pH so much'?

See my first post upthread, OW.

Al

^ oh I see, so for plants in the ground rather than in containers, you would use something like vinegar or citric acid in the irrigation water to raise the pH rather than adding peat moss or sulphur? I thought you just were referring to container plants.

Lol - you were referring to 'in-ground' plants? I'm confused. ;-)

Al

Wow... good point Al. I totally forgot about that. *whoosh*

OW - Don't you mean.. lower to 6? If you have a way to directly measure the pH, then it doesn't really matter what kind of water you use. Just add the vinegar or acetic acid until you get the desired pH for the irrigation water.

If you don't want to mess with the irrigation water, and you're okay with an imprecise change, you could use acidified cotton burr compost. It contains sulfur that is at least partially metabolized, and is often used as an acidifying soil amendment for Roses and Azaleas. It's commonly used both in the ground, and in containers. I don't know much about it, but you can find plenty of information online.

I'm confused, are soil from your land in the containers? Or do you also want to try growing blueberries in the ground, and want to acidify the soil quickly? If you're using raised beds and adding a lot of new soil / amendments, most good nurseries sell an Azalea or Rose bedding mix that is fairly acidic. The quick fix is ammonium sulfate, but it's extremely hard for the non-professional to use properly, and is very detrimental to your soil biology.

No amendment or product can really change your soil's pH permanently - you have to keep treating it at least every season.

^ yes, sorry I haven't been very clear - I apologise. Just to clarify, first I was asking about sulphur in containers and then I started to ask about the soil in the ground in my allotment. And yes, I did mean 'lower' rather than 'raise'!

The soil in the ground in my allotment earth/soil is pH 7 and I want to lower it to pH 5-6.5. Because I am planting very soon (I have to plant many of my plants in the ground now, since it's April), I don't have time to wait for the sulphur to break down and lower the pH. So, I was wondering whether I could use peat moss alone? If so, how much should I use?

I will be planting blueberries as well as lots of other plants that require a pH lower than 7 but not as acidic as the blueberries, hence the reason why I wanted to get it to pH 5-6.5.

Oh and just to add, I'm not using raised beds. I'm actually going to be using the soil on the allotment itself.

You're not going to get any significant movement in soil pH by adding anything organic, like peat/bark/other because of the high buffering capacity of the soil. You'd do best to see your county extension agent for recommendations based on a soil test.

Al

^ I will do that tomorrow if I can (I'm not sure if we have county extension agents in the UK though?), but tapla, failing that if I can't get an answer, I guess it'll have to be sulphur then? I understand it will not be a long term solution, but if I do it regularly every year, it could allow me to grow blueberries and raspberries in the soil?

Actually after thinking about it, it sounds as if I'm just not going to be able to grow blueberries in the pH soil, even if I use sulphur, so I'm probably going to have to use a raised bed with a lot of peat moss (maybe 50/50 peat moss and topsoil) or just containers unfortunately.