Seaweed as Fertilizer?

[OldGuy43]

I was watching BBC's "The Edwardian Farm" and they were using seaweed for fertilizer in their market garden. They would go to the coast and collect seaweed, spread it around and plow it in. Wouldn't the salt be a problem?

 

[so lucky]

I would think so. But maybe it is not as saline as we think. I have used "liquid seaweed" fertilizer in the past. I didn't know if it was de-salted or not. I guess all the other minerals in sea water would be a good thing.

 

[Ridgerunner]

I havent used seaweed so no experience with that. And I have not seen that show. I dont know if they get the salt out or not. Sometimes they omit some of these details. It is TV.

Kind of reminds me of a thread over on the chicken forum a couple of years back. We were discussing using chicken manure on a garden. One poster fairly early in the thread said they had been using it in their garden for years. Some of us started talking about the risks of using pure fresh chicken manure directly in a garden. That poster came back and said, Well yeah. I compost it first. A little detail that can make a big difference.

I dont know how salty that seaweed is to start with, whether they let it rain on it before they use it, details like that. Theres another thing. Salt is pretty water soluble. If it rains a lot and that water can drain off, a lot of salt will leach out. A lot of problem with salt build-up is where the water doesnt run off but soaks in.

Salt build-up can be a problem on irrigated fields where the water soaks in instead of runs off. Im sure that if they are using that seaweed there is something about how they use it or some technique where salt is not a long-term problem. But I dont know the details about how that works out.

 

[so lucky]

I would guess that the salt buildup in fields that don't get good drainage is similar to the "salt" buildup in flower pots that don't get thoroughly flushed occasionally. It is not really salt, sodium chloride, but a mixture of all the minerals present in our water that have leached out over time. I don't know if this buildup is harmful to the plant, but it does look unsightly on the pot and soil. In my very hard water, it takes just a matter of a few days for this white, tan, or orange residue to become apparent. Yuk.

 

[catjac1975]

We used to get a lot. Loaded with trace minerals.

We rinsed it out while still in the truck.