This investigation will help you to:
Constructing a Set of Soil Sieves,
Maine Geological Survey
This site provides instructions for making a set of different mesh screen strainers.
Organic Matter in Soil, USDA-NRCS
This site reviews the basics of organic content in the soil of your backyard garden.
Soil Quality Indicators, NRCS
This PDF (you must have Adobe Acrobat to view this file) explains how organic material is incorporated into soil and why it is important.
Soil Minerals, Forest Preserve District of Cook County (Illinois), NEWTON
This online article reviews the major constituents of soil, with a focus on the elements which are essential for plant growth.
Soil Components, University of British Columbia
Discusses five basic components of soil: air, water, minerals, organic matter, and biology.