Dupont recalls Imprelis. Active ingredient is in a class of herbicides whose contamination of composting feedstock (both plants directly treated and manure generated by livestock that have eaten treated plants) have resulted in death of plants grown in such compost-mended soil. View Persistent Herbicides in Compost.
Other items of interest
Teaming with Microbes: A Gardener's Guide to the Soil Web. A book by Wayne Lewis and Jeff Lowenfels
The New Organic Grower. A book by Elliot Coleman
The Soul of Soil The Best of Fine Gardening - Health Soil. A book by Grace Gershuny and Joe Smillie
Organic Soil Fertility Management. A book by Steve Gilman