Links
Soil Science Society of America
http://www.soils.org/Crop Science Society of America
http://www.crops.org/American Society of Agronomy
http://www.agronomy.org/Manure Analysis Proficiency Testing Program
http://ghex.colostate.edu/map/Compost Analysis Proficiency Testing Program
http://tmecc.org/cap/Soil and Plant Analysis Council
http://www.spcouncil.com/AOAC
http://www.aoac.org/Canadian Soil Science Society
http://www.csss.ca/