Heh, no fear of me not using the kelp, six ways from Sunday.
I love the stuff and as you rightly said it's free.. and a great excuse to go to the beach.
I do use it in compost, and it makes the best mulch for my garlic.. no weeds and whatever breaks down they seem to love it. I also let some kelp rot down for a year in a bag, from time to time, after which it is stored as a powder, more or less water soluble goodies for various TLC purposes.
About the 'professors', are you sure they're not turning up their noses on principle and without good reasons? It wouldn't be the first time that I heard scientists scoff just because they heard some other authority say so, and took it on 'authority' alone and/or out of context, without basing their claim on any actual data.
My best guess is that 'comfrey tea' in the recommended dilution etc was not found to have an amount of nutrients equivalent to some other liquid fertilizer ie strong enough to have effects. Just as the 'kelp extracts' which are sold for mucho dinero are used so dilute that they have only a hormonal effect but no significant or measurable nutrient contribution. That doesn't mean there's no potassium value in bulk raw kelp, obviously.
I think a dry comfrey leaf probably doesn't weigh much and it would take a lot of em to make a pound of 'comfrey ferts', with the label value of NPK that was found in that legitimate study, quoted by Rodale. Weak tea is a whole other matter, of course it won't have the same value if it's mostly water. I think I'd be tempted to try the other method described in the Rodale article, just weighting down the raw leaves and letting the rotted liquid drain into a bucket below, then bottle and dilute for use as we do with eg fish emulsion to keep from burning the plants. The liquid product before dilution should have a nutrient value close to or equal the measured value for dried leaves in the study.... and it's not bad, it's certainly comparable to the values listed on my fish e bottle or my dry chicken manure stuff. Which are not free, like a heap of otherwise useless comfrey would be free.
For the labour of making it.
If the actually measured NPK value of raw comfrey material is disputed by the 'professors' on scientific grounds, I'd be interested to hear about that. I haven't seen or reviewed the methods used in the cited study, I'm taking on faith that the science was properly done.
