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Show VII. Find Out How Much Alive Soil Is Take 3 large, heavy paper shopping bags, a ruler, a small spade, and 6 or more small bottles with lids or corks. A small magnifying glass will also be helpful. Measure off an area 1- foot square and collect the soil to a depth of 2 or 3 inches from each of the following places: 1. Below the leaves in an ungrazed and un- burned woodland. 2. A pasture or fence row, just below the surface. 3. A badly eroded field where subsoil is exposed. As you remove the soil watch for burrows of worms and other animals. You may also find the eggs of certain insects singly or in masses or pods. Examine the samples, either indoors or outdoors. If you examine them indoors, small specimens will not be blown away by the wind and you can use a microscope to look for small organisms. Pour out the samples on separate sheets of white paper the size of an opened newspaper. Carefully sort the soil, watching closely for small Jiving things. One- foot squares of 14- inch hardware cloth or window screen will be helpful in making this examination. Place the different kinds of animal life in separate bottles. Count the animal life belonging to each of the following groups: 1. Worms ( such as earthworms or night crawlers having no legs). 2. Grubs ( any wormlike animal with legs). 3. Snails. ( Snails without shells are called slugs.) 4. Insects ( any hard- shelled, soft- bodied, or winged ( not all have wings) animal with 3 pairs of legs). 5. Spiders, mites, ticks, ( animals with 4 pairs of legs). 6. Animals with more than 4 pairs of legs. 7. Others ( any animal not falling into one of the above groups). Which soil sample has the most small animal life? Does this seem to be related to the rate these soils absorbed water in Activity IV? Does the amount of animal life and the burrows the animals make appear to have any relation to the looseness of the soil ? Figure the total number of animals per acre for each group from each of the sampled areas. ( There are 43,560 square feet in an acre.) Also figure the grand total of all of the animals for 1 acre. No matter how large the total number of visible animals you find in the soil, it is small compared to the number of microscopic plants and animals, particularly bacteria, present. This activity is best suited to spring. INTERPRETATION The soil is the home of innumerable kinds of plant and animal life that range in size from those too small to be seen with a powerful microscope to large ones such as earthworms. Most of the living organisms in the soil are so small you will not be able to see them without a microscope. These living organisms have a marked effect on the characteristics of the soil itself. At the same time, such soil characteristics as the granulation ( structure) of soil, how well air moves through it, how wet it is, how much organic matter it contains, whether it is sweet or acid, how the farmer handles his soil, all strongly affect the number of organisms in the soil. Plantlife that is too small to be seen without a microscope includes bacteria, fungi, and algae. Bacteria, 1- celled organisms, alone may be present to the extent of 1 to 4 billion per gram of soil. Fungi, which include molds, do not contain chlorophyll and therefore cannot manufacture their own food. A gram of soil contains from 8,000 to 1 million of these. Soil algae are microscopic plants that contain chlorophyll and may run as high as 100,000 per gram of soil under favorable conditions. Animal life in the soil includes protozoa, microscopic animals larger than bacteria; nematodes, larger and more complicated than protozoa but some still too small to be seen without a microscope ; and earthworms, ants, snails, spiders, mites, and various other worms and insects. It is only specimens of this last group, and possibly some of the larger nematodes, that you will see in this study. Earthworms are the most important group of the larger animals. They live in soils that are high in organic matter and not too sandy. The number of earthworms may range from a few hundred to more than a million per acre. Under favorable conditions between 200 and 1,000 pounds of earthworms may be present in an acre of soil. The earthworms in an acre of soil pass several tons of soil through their bodies each year and in so doing make certain nutrients available to plants. Burrows left by earthworms let water and air move 9 |