Reddit reviews Teaming with Nutrients: The Organic Gardener’s Guide to Optimizing Plant Nutrition

One Straw Revolution

Teaming with Microbes

Teaming with Nutrients

Master Cho's Lessons

Gaia's Garden

This is a good base into the natural side of things, if that interests you at all.

I have read all of these front to back multiple times. I read the grow bible 5 times before I even started purchasing equipment and propagating seeds. Do it right, take the time to do the research. You will find there are many cost effective ways to grow amazing Cannabis.

True Living Organics: The Ultimate Guide to Growing All-Natural Marijuana Indoors

The Cannabis Grow Bible: The Definitive Guide to Growing Marijuana for Recreational and Medical Use

Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web, Revised Edition (Science for Gardeners)

Teaming with Nutrients: The Organic Gardener’s Guide to Optimizing Plant Nutrition (Science for Gardeners)

Fundamentals of Horticulture 4th Edition

The Secret Life of Plants: a Fascinating Account of the Physical, Emotional, and Spiritual Relations Between Plants and Man

edit: If you cant tell I am an organic cultivator. ;D

Whether or not your 'flush' was needed depends on what was in your fertilizer as you were using bottled chemicals and not organic inputs... Organic gardening relies on organic inputs decomposing in soil via microbial activity, broken down and fed to plants through a mycorrhizal fungal network. You don't need to use any sort of bottled nutrients if you are gardening organically. I'm no expert gardener, but I've worked in a few gardens and harvested a few plants, and I seem to see the healthiest, hardiest plants grown in plain soil with no bottled nutrients. Check out the book "Teaming with Microbes" by Jeff Lowenfels and explore the soil food web http://www.soilfoodweb.com/ if you want to learn about organic gardening. If you want to learn more Jeff has written a three part series, the next book is Teaming with Nutrients and lastly Teaming with Fungi.

I'm going to read Teaming With Nutrients next; Korean Natural Farming is awesome if you're willing to put in the time, and you have the space for fermenting stuff.

You're definitely wise to approach things as a skeptic. I was talking with a fellow permie once about all kinds of permie things, and I thought they seemed quite rational. Then, they started talking about energy healing. That was a "smile and nod" moment. I swear, we're mostly sane.

Teaming with Microbes and Teaming with Nutrients might be helpful books to check out. They don't directly address mineral accumulation, but it explains the processes through with accumulation occurs, if that makes sense. They're very thorough books that will make you wish you had paid more attention in Bio 101, but they're written in an engaging way.

This study is on bioaccumulation, though they're testing for heavy metals and not nutritional value. Maybe their methods are explained.

As far as comfrey goes, I know it dredges up minerals from the subsoil with its remarkably long roots. As the leaves die, they decompose on the ground and the minerals become available in the topsoil, which then makes those minerals available to other plants who don't have such deep roots.

Legumes, however, have bacteria colonies surrounding their roots that make nitrogen from the air available to the plant. When the plant dies, it decomposes and then the air-harvested nitrogen becomes available in the soil. Usually, we innoculate legume plantings with the bacteria. It occurs naturally in soil, but may not necessarily be present in every square foot of soil. So, better to be safe than sorry.