Stinking concoction

My son is a novice gardener. He is probably never going to progress much beyond this status. He read that comfrey made good fertiliser so plucked the leaves from plants around his compost bins and soaked them in a bucket of water. The smell was so bad that he was forced to apologise to his neighbours! He has vowed never to make it again but dispersed the offending bucket full around his tomato plants. I'm not sure I want any of this harvest now!