I've been doing a bit more reading about growing plants hydroponically. In doing so, I found reference to something called "Hoagland solutions", which are nutrient solutions used for growing plants hydroponically. Since hydroponically grown plants don't get nutrients from trace elements in the organic matter in soil, you need to be especially careful to ensure that plants get adequate nutrition, and Hoagland and Arnon well apparently one of the first to document solutions that work. In digging up references, I found this PDF of their 1950 work on the subject. It's very interesting, if somewhat harsh in debugging myths about hydroponics. They also document a bunch of nutrient solutions that one can use to study mineral difficiencies of various types, each one lacking some essential nutrient. Anyway, it's very interesting, so I stashed it on Google Docs, and if you chase the link below, you can see (or share) a copy of the document.