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questions about collecting seagrass and seaweed for soil building

 
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Along the shorelines, I often find turtle grass washed up; if a storm system churns up the ocean over the Sargasso Sea, I tend to find piles of sargassum weed two or three days afterward.

Now, in theory, every rainy season, our soils lose minerals to the sea, right? Rains dissolve soil minerals and wash them out. The rivers on the North Coast are very flashy, i.e. they become raging torrents after rain, and during those times, are generally the color of a latte, from the suspended sediments. So bringing marine vegetation back up to the ridge top should help to restore the soil minerals, if done on a large enough scale. My worry was that this might expose the plants to too much salt; but on the small scale I have been able to experiment with this, I find no evidence of damage.

I do wonder whether the turtle grass, from inshore waters, has a different trace mineral content than the sargassum, from far out at sea? More importantly, I wonder how much of this marine vegetation I need to make a difference in soil mineral content, and how much is too much? I really don't know any way of testing this.
 
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Dr Bryant Redhawk has some excellent info in the soil forum regarding seaweed and seawater.
 
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If you think of minerals as existing on a supply chain, the beginning of that supply chain is volcanic activity. Molten rock is sprewed from underground, and is broken down by erosion, wind, water, digestion enzymes, over and over, through several trophic levels, transported over the landscape until it eventually ends up in our waterways at the end of the supply chain, the ocean.  

That's why garden stores carry products like volcanic rock dust, or kelp meal. These products contain the "full spectrum" of minerals.  

Adding seaweed and seawater (properly diluted) to your soil is a great way to remineralize it.  In addition to the geology, you also need the biology to process these mineral into plant-available forms.  You can think of your soil microorganisms as supertiny crawling bags of nutrients. A healthy soil food web will contain the minerals as well as the means to transfer them from organism to organism, so things are not washed away in a heavy rain event, or sitting inert with no possibility of uptake.
 
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I will just say that most commercial chemical fertilizers will have a much higher salt content than the seaweed you speak of. That being said, a simple freshwater rinse would probably remove any salt, but may also remove those valuable minerals lost to erosion. My general rule of thumb is to only apply diluted seawater to my garden twice a month, so I would think you will be fine to add this.
 
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Jason Hernandez wrote:Along the shorelines, I often find turtle grass washed up; if a storm system churns up the ocean over the Sargasso Sea, I tend to find piles of sargassum weed two or three days afterward.

Now, in theory, every rainy season, our soils lose minerals to the sea, right? Rains dissolve soil minerals and wash them out. The rivers on the North Coast are very flashy, i.e. they become raging torrents after rain, and during those times, are generally the color of a latte, from the suspended sediments. So bringing marine vegetation back up to the ridge top should help to restore the soil minerals, if done on a large enough scale. My worry was that this might expose the plants to too much salt; but on the small scale I have been able to experiment with this, I find no evidence of damage.

I do wonder whether the turtle grass, from inshore waters, has a different trace mineral content than the sargassum, from far out at sea? More importantly, I wonder how much of this marine vegetation I need to make a difference in soil mineral content, and how much is too much? I really don't know any way of testing this.



Land minerals tend to be limited to around 75 different minerals, these can be tested for chemically and have been identified by those processes.
Sea water usually has around 95 minerals, so sea water has 20 minerals not found in soil that is on dry land.

Now that we know that there are differences between sea minerals and land minerals, it should be easy to see that fresh water items would not have the same mineral makeup since fresh water would be missing at least 20 minerals found only in sea water and sea plants.

As long as you are not doing anything to concentrate the sea weeds, it would be very difficult to over use the marine vegetation, and you don't need to rinse it off, in fact, it is better to not rinse sea weeds prior to use on land plants.
Contrary to what most seem to believe, sea salts do not "salt up' the land, you can flood land with sea water, this is actually done in several countries to get the soil re-mineralized for planting.
Studies have been done and we know you can put 28000 gallons of sea water on one acre of land with no ill effects to the microbiome, which means the plants in that soil will do fine as well.

Redhawk
 
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