21. They conduct research in irrigation and drainage, tillage, soil classification , soil fertility, and other areas. 22. Canadian soil scientists required a new method of soil classification that focused on pedogenic processes in cool climatic environments. 23. At the top, most general, level of the Australian Soil Classification , there are fourteen soil orders. 24. The World Reference Base for Soil Resources ( WRB ) aims to establish an international reference base for soil classification . 25. The most common engineering classification system for soils in North America is the Unified Soil Classification System ( USCS ). 26. Under the Australian Soil Classification they can be included in different orders such as Podosols, Sodosol, Chromosols or Kurosols. 27. The process for grading a soil is in accordance with either the Unified Soil Classification System or the AASHTO Soil Classification System. 28. The process for grading a soil is in accordance with either the Unified Soil Classification System or the AASHTO Soil Classification System. 29. The process of grading a soil is in accordance with either the Unified Soil Classification System or the AASHTO Soil Classification System. 30. The process of grading a soil is in accordance with either the Unified Soil Classification System or the AASHTO Soil Classification System.
