Seaweed, sulfur, and acidic soil

leira(6 MA)May 3, 2012

I understand that seaweed is a great addition to compost, or to garden soil.

I have access to copious amounts of seaweed, but it's a variety that's known for its particularly high sulfur content (you can smell it from quite a distance on the beach, and I can track down the species name if anyone thinks it would be helpful).

I also live in an area that has acidic soil.

As I understand it, sulfur is commonly used to lower the pH for people who have alkaline soils. Lowering the pH is certainly not what I want to be doing.

So...should I give up on the idea of trying to incorporate this particular seaweed into my compost or garden beds? Should I use but try to balance it out with lime? Am I worrying unnecessarily?


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toxcrusadr Clay Soil(Zone 6a - MO)

It's a good question that I don't have a definitive answer to. But I can say that the sulfur in the algae is most likely from sulfur compounds rather than elemental sulfur (which is what is used to lower pH). So it is not automatic that it will have the same effect. If composted first, the composting process *should* drive all organic matter towards neutral pH. I'll confine my answer to that and see if anyone else chimes in.

    Bookmark   May 3, 2012 at 10:27AM
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I have never heard of any seaweed acidifying soil.

    Bookmark   May 3, 2012 at 7:13PM
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What seaweed is it? I use rockweed and eelgrass with excellent results.

    Bookmark   May 8, 2012 at 7:28AM
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leira(6 MA)

The seaweed (really an alga, apparently) is Pilayella littoralis.

There's apparently a journal article titled "Isolation of humic acid from the brown alga Pilayella littoralis" which I'd love to read, but I don't really care to spend $35 for the privilege.

    Bookmark   May 9, 2012 at 8:34AM
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bluegoat_gw(Zone 3b)

I doubt very much if the little bit of sulfur in the algea will change the pH of the soil. The addition of calcium carbonate will easily neutralize any possible pH change and also add an important nutrient to the soil. If you use the algae in your compost, avoid adding CaCO3 to the compost since it causes a loss of nitrogen.

    Bookmark   May 9, 2012 at 10:45AM
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It always amazes me when people spend that much time and energy trying to find ways to dispose of "waste" materials without thinking that maybe this could be used in gardens. After some 40 years your DCR should have some idea of what affect this algae would have on soil and whether the sulfur compounds might affect soil pH.
Since things such as tree leaves and pine needles do not lower soil pH I would doubt that this algae would either.

    Bookmark   May 11, 2012 at 7:06AM
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toxcrusadr Clay Soil(Zone 6a - MO)

What's a DCR?

    Bookmark   May 11, 2012 at 5:14PM
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leira(6 MA)

toxcrusadr, the DCR is the Massachusetts Department of Conservation and Recreation -- the oldest regional park system in the United States. They oversee quite a bit of public land.

Here is a link that might be useful: DCR

    Bookmark   May 11, 2012 at 5:32PM
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I got a hold of some of that seaweed (I think we call it 'Mung' down on the Cape), and I would be eager to add all I can to my garden soil. Maybe let it sit in a pile for a while to leach salt out first, or add it in as a compost green. I expect it would mix very well with leaves or similar browns.

    Bookmark   May 24, 2012 at 9:29AM
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Seaweed in small doses for micronutrients-good- seaweed as a carbon source-???. Kelp, for example, in generous servings, contains excessive salts, growth hormones, and anti-mychorrhizal properties. That's my final answer, Chuck. We use kelp extract anually, but the amount of seaweed contained in the yearly application is *tiny*.


    Bookmark   May 24, 2012 at 10:23AM
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blazeaglory(10 SZ22/24 OC Ca)

Didnt growers of old in Ireland used to grow their potatoes straight in seaweed on the land?

    Bookmark   May 24, 2012 at 9:21PM
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They all came over here cuz they monocultured potato, arrived and disovered tomato, and the yankees amongst 'em call it "pototto". Little known to the English, the Russians came up with the secret to potato ("Vodka"), then some of the Irish intermarried, and now we have the bloody mary...


    Bookmark   May 24, 2012 at 9:36PM
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