I live fairly near the sea and have gathered several bags of seaweed - mostly kelp - from the beach. What is the best way of using this, should I compost it, use it as mulch or what? Which crops will benefit most from it?

I've just sown a few tomatoes, peppers and greyhound cabbage in boxes under plastic on top of the boiler (free propagator!). It's probably too early but I can always put some more in later. They may be OK if the weather's OK, but it won't be a great loss if they fail.