Using Cover Crops in Oregon, a sample of an Oregon State University extension publication EM8704, reprinted October 1998 and available for purchase. Sample chapters: Annual Ryegrass; Barley, Oats, Triticale, Wheat; Buckwheat; Cereal rye; Common vetch; Crimson clover; Fava bean; Field pea; Hairy vetch; Rapeseed; Red clover; Subterranean clover; Sudangrass/sorgum-sudangrass hybrids; Nitrogen scavenging; Cover crop weed suppression in annual crop rotations.
UC SAREP Cover Crop Resource Page, University of California Sustainable Agriculture Research and Education Program.
Forage Information System, Oregon State University, Crop and Soil Science, the mother-load of all information on forages.
Managing Cover Crops Profitably, 3rd Edition. This comprehensive book explores how and why cover crops work and provides all the information needed to build cover crops into any farming operation.It includes information on cover crop species: legumes, nonlegumes and grass-legume mixtures. Revised 2007, 244 pages pdf.
Overview of cover crops and green manures, Preston Sullivan, Appropriate Technology Transfer for Rural Areas (ATTRA). July 2003.