Soil Genesis and Development, Lesson 6 - Global Soil Resources and Distribution Glossary

(i) The total mass of living organisms in a given volume or mass of soil. (ii) The total weight of all organisms in a particular environment.

Permanently frozen material underlying the solum.  (ii)  A perennially frozen soil horizon. 

Management of soil and crop cultural practices so as not to degrade or impair environmental quality on or off site, and without eventually reducing yield potential as a result of the chosen practice through exhaustion of either on-site resources or non-renewable inputs.