this "1" means 1%. You should take care with the other 99% in this case. For example, if you use too much of this thing you might not get a problem of over do in K, but the other 99% are made of what? is that a problem to have too much of that on the ground? I do believe kelp isn't a problem at all, but it could contain much salt or anything else.
What you could do for K is buy one banana, only one, and slice and put on the water, the next day you water with that... and you are done.