it was suggested by British Oxfam worker Bill Hereford in the beginning of the 1980s. See also George Washington Carver Soil conservation Tillage erosion References External links NRCS Conservation Practice Standard 330-Contour Farming 4 page pdf file American Experience page on the dust bowl Encyclopædia Britannica page on contour farming Purdue University article on contour farming Natural Resources Conservation Service page on sustainable farming Manitoba Soil Conservation Resource Manual Priority One. Together We Can Beat Global Warming Pearce, F. (2002) Africans go back to the land as plants reclaim the desert, New Scientist 21. September, page 4. Looking after our land - Soil and Water Conservation in Dryland Africa - Detailed instructions for contour bund construction. BBC News - Sahara desert frontiers turn green -Article on Water Erosion from Penn State College of Agricultural Sciences -Article on Tillage Erosion from Penn State College of Agricultural Sciences Agricultural soil science