RT Journal Article SR Electronic T1 US agriculture's relationship to soil carbon JF Journal of Soil and Water Conservation FD Soil and Water Conservation Society SP 159A OP 165A DO 10.2489/jswc.64.6.159A VO 64 IS 6 A1 Ronald F. Follett YR 2009 UL http://www.jswconline.org/content/64/6/159A.abstract AB