Dr. David Hopkins
Address: North Dakota State University
Soil Science Department
Bolley Drive
233 Walster Hall
PO Box 5638
Fargo, ND 58105
Phone: 701-231-8948
Fax: 701-231-7861
email: david.hopkins@ndsu.nodak.edu

"When I add up the live weights, exclusive of roots, estimated by soil biologists, I find more living biomass below the ground than above it, amounting to the equivalent of 12 horses per acre. The soil organisms consume oxygen from the soil air and give off carbon dioxide, and the summation of the multitudes of respirations characterizes the metabolism of a soil individual. Hence I designate soil as a living system."

Hans Jenny, "My friend, the Soil", Journal of Soil
and Water Conservation, 1984, p. 160