If you work with compost, you are already familiar with the process of separating organic material from soil. This process is similar to separating finished and unfinished compost. Archaeologists also follow this process when they are searching midden pits for debris that can tell us about people who came before. Since organic matter has clumping characteristics, it can easily be separated from soil through the action of screening with sieves.
Separating Finished and Unfinished Compost
Pick out any large clumps of organic material from your soil pile and place them in a 5-gallon bucket.
Using a trowel, scoop soil from your soil pile into your sieve. Place the sieve over a second 5-gallon bucket.
Shake the sieve back and forth to allow soil to pass through the sieve and into the bucket. Then transfer the remaining organic material into the first 5-gallon bucket.
Repeat this process until the finished soil is separated from the unfinished organic material. Return the large organic material to the compost pile to finish breaking down into soil. Mix the soil into your garden.
Separating Organic Particles for Study
Pick out any rocks from your soil sample.
Transfer soil to your sieve with a 1-inch screen and shake the sieve back and forth over a bucket. Place the large organic material that is caught in the sieve into a plastic bag and label with a marker.
Place the soil from the bucket into a sieve with a ½ inch sieve and shake it back and forth over the second bucket. Put the organic material that is caught in the sieve into another plastic bag and label with the marker. Repeat this process using smaller and smaller sieves.
Fill a bucket with water and dump the remaining fine soil into the water. Wait for the organic material to float to the surface and the soil to sink. This process may take between 24 and 48 hours.
Strain the organic material off of the top of the water bucket using a dipper. Pour the dipper of water through a cheesecloth to separate the water from the organic material. Allow organic material to dry, and then place into a plastic bag and label.
Allow soil to dry, place it in a bag and label it for further analysis.