Reducing the acidity in peat moss based potting soil

I would use the coco fiber but I don't have any at this time so I'm using the bags you buy at Home Depot, Miracle Grow, etc.

If I water the soil with a little bit of calcium bicarbonate, will that balance the pH? How much should I use? Is it safe for the plants?

You don't mention whether this is a new bag of potting mix, or if you're already growing things in it. Any time you buy a bag of potting mix that contains a slow release fertilizer, it's probable that the fertilizer has already released because of the high temperature of the bag (most slow release fertilizers release based on soil temps, the higher the temp, the faster the release). If you haven't used the soil yet, put it in a container that will drain well and flush it out with clear water to get rid of any accumulated salt buildup. Your pH should be within an acceptable range without further amendment. When I buy a peat based mix, I generally stick with FertiLome's ultimate mix, without fertilizer. That seems to give me the best results and is a very consistent product. Lambert Peat Moss makes the FertiLome mix, and they harvest some pretty nice peat.

??? What does all that have to do with the pH? Peat is naturally very high in acidity.

I don't know of any soilless mfr. whose media isn't already in the middle range of pH as the product leaves the factory. I've grown plants at the far ends of the pH range and really never had a problem. That's why I asked if you were dealing with a new bag.

illiniguy- Thanks for the info regarding the loss of fertilizer in the bags. I didn't know that.

You're better off just buying a non-fertilized mix (again, I've not found any better peat based mix than FertiLome, which may not be available in your area) and do your own fertilizing. If you can find coconut coir, it's got a lot better water-holding ability. A lot of places sell compressed coir bricks, which you can hydrate and add to your containers. I'm doing a tomato trial now using a product called Wonder Soil, which is primarily coir with just a little bit of peat, and I'm very happy with the way it's holding water here in the heat of mid Missouri. To maintain complete control over all the inputs, I'm growing them in Topsy Turvy planters which are hanging in direct afternoon sun, and have only added 3 cups of water all week. The plants look very happy.

This is very frustrating...

Sorry about that. I know this is your thread, and I didn't want to step on your toes or get you off track. I'll take my comments elsewhere. Best of luck.

No, I'm sorry. I must have gotten off the wrong side of the bed or something. Not your fault. I apologize for my rudeness.

Are you using a peat based potting mix or are you using peat and mixing your own? AFAIK, all potting mix will contain pH adjusters to bring the pH to near neutral. I looked at the web site for Pro-Mix and it contains limestone. I could not see any ingredients listed in MiracleGro potting mix, though I spotted this on their website:

"Potting Soil and Amendments: Our potting soils are the ideal mix of organic materials, sphagnum peat moss and perlite, pH balancers and wetting agents plus nutrients."

- Brent

What I've learned is that when the mix is new, the ph is fine. The original Ph of the peat is very acid so that is why it's adjusted when the potting mix is created for sale.
Over time, the constant leaching of the soil washes away the "Ph adjusters" and causes the ph of the peat to return to it's original acid level, so that's when the problems come.
When I tested my older pots thety were very acid. I used lime very sparingly and didn't have any problems... I just couldn't fertilize for a month or two.
The process of the Ph becoming acid seems to be excellerated if you fertilize a lot.
I'm no expert, this is just what I learned from DGrs and personal experience. Hope this helps!

Hmm. I just used a lot of peat to amend heavy sandy clay soil (I know that makes no sense, but that is what it seemed to be) in a new bed. I didn't add lime because my soil is usually very alkaline. I wonder if I should have . . . . and if it is too late to broadcast it on top, since I've already dug in the plants. I didn't remember that peat was so acidic.

I wonder, happy, if you would have trouble getting an accurate pH reading righ away, before things have worked together awhile. Your soil is usually alkaline?? I'm surprrsed for our area. I would keep an eye on the plants, of course. I bet you're OK.

I was stunned that my soil was alkaline. For years, I kept dumping lime on it without checking -- but it is alkaline even in areas that I never touched with lime.

CaptMicha: Is it possible to get the coco fiber locally (in Maryland)? I've never seen it.

Sounds to me like you need a proper soil test, by either a gizmo you can buy or your regional authority.

But I'm intrigued by the idea of adding simple bicarbonate of soda to your watercan. What's people's experience with this as a temprorary or even long-term solution to high soil acidity? I live in a pine forest area, so this is an ongoing problem.

I would add wood ash to make the ph more alkaline. Won't wash out as quickly.

We don't have a fire, but we could buy baking soda. Would it work?

Why not add lime?

I don't know about baking soda. Lime would work.

I have the opposite problem and am forever adding acid ingredients to my limestoney soil.

I'm thinking (guessing) that baking soda is too soluble (release all alkilinity at once) and/or more expensive than lime

"CaptMicha: Is it possible to get the coco fiber locally (in Maryland)? I've never seen it."

I don't think so. Maybe Johnsons has it or a hydroponics store??

I have looked at Lowes, HD and a local farm supply and not seen it. Pinetree Seeds has been carrying it.
They are currently sold out; I just checked.

This message was edited Nov 13, 2007 11:05 PM

HD here in Ottawa sells coir, but each region has its own buyers and hence different product lines available.

As for using lime to sweeten acid soil, I use dolomite granules on the lawns and gardens every 2-3 years. My question about baking soda was moree for containers or spot-sweetening for plants such as delphiniums or clematis.

The standard container soil amendment to adjust pH northward is dolomitic lime, which adds Ca and Mg at the proper ratio (these nutrients are mutually antagonistic, and an excess of one effects the uptake of the other). NaHCO3, while it will work on an ongoing basis to raise pH, just adds useless ions to the soil and increases total dissolved solids in soil solution. Increasing TDS (and its accompanying electrical conductivity - EC) makes it more difficult for plants to uptake water and dissolved nutrients. I can explain in more detail if you wish .....

If you were able to monitor the TDS and EC of your soil solution, you would find that you would be able to use far less fertilizer (the reduction in TDS from fertilizer, which contains usable nutrients, would be equal to the TDS in the NaHCO3 solution you added to adjust pH, which as noted, contains elements useless to the plant) when adding the soda solution. So, even if you maintained a favorable level of TDS and EC in your soil solution, since you cannot use as much fertilizer, there could easily be nutrient deficiencies on one end of the spectrum, or if you attempt to maintain nutrients in the 'adequacy range', plasmolysis (fertilizer burn) on the other end.

I'd stick with the dolomite. Why did you say you felt you needed to increase pH? Do you know what the media pH is now? A high % of plants do VERY well in containers at pretty low pH, btw.

Al