Figure out what your soil needs:
The Dirt on Soil Testing, RAFI’s guide to testing your soil
OrganiCalc, an online worksheet for calculating the right quantities for soil amendments
Learn about soil amendment strategies:
Soil Health, Natural Resources Conservation Service (NRCS)
Strategies for Farm Soil Amendment, Carolina Farm Stewardship Association
Choosing a Soil Amendment, Colorado State University Extension
Sourcing Soil Amendments for Small-Scale Farms and Gardens, University of Georgia
Using Less Fertilizer Might Pay Off in Unexpected Ways, Morning Ag Clips