Some people say rinse to remove the salt, some people say don't bother...I would go ahead and rinse since its easy to do.
Kelp breaks down easily so you can use it as a mulch in a 2-4 inch layer or throw it in with your compost. You can also make a kelp tea by adding a few handfuls of kelp to a 5 gallon bucket of water and let it sit for a few days, stirring daily, then strain out the kelp and dilute it to 1 part kelp water to 2 parts water. You can use this as a liquid fertilizer or as a foliar spray.
Kelp is awesome, it adds the complete range of trace minerals plus hormones which increase resistance to stress. And, its free!
As for harvesting, I would just walk to the beach and see what's washed up, if that fails I suppose you could boat out and try to pull some up but I've never tried that.
Kelp is great fertilizer. Along with trace elements and abundance of Potash, it also contains growth stimulants for plants. All seaweed has a good resistance to drying out though so, I'd mix it in the compost and then spread it. One thing you don't want to do with kelp is use it to fertilize Broccoli, Cauliflower and any plant you eat in it's entirety. The potash makes very strong stems and as such it makes the stalks really woody and tasteless. Ever had broccoli and the stems were like eating tooth pics and you had to spit it out? Too much potash is one reason. It is good for hay that has lodging problems though.
John Meshna (owner)
Blue River LLC
1195 Dog Team Road
New Haven, Vt 05472
Also, does anyone know anything about contamination in kelp? The water around here is pretty polluted and I've been wondering if that could be absorbed by the kelp and possibly bad to put in the garden..any thoughts?
Companion Planting Guide by World Permaculture Association