The Great Plant Escape

Case 2 - Background Information

Once you step out onto a piece of ground, you step out onto a very active piece of real estate. Soil is not just a piece of dirt. Soil is a complex system composed of living and nonliving material spread as a very thin layer over the entire surface of the planet we call earth.

Soil is not just the surface, however, but the entire depth as it affects plant growth. Soil must provide nutrients, water, and air and helps to support the plant.

Four major components of soil

The part of the soil we spend most of our time talking about is the solid part or mineral matter. This solid matter makes up about 45 percent of what we call soil and is composed of three particles: sand, silt, and clay. Equally important, however, are air and water. The two together account for about 50 percent of soil. The percent of each depends on how much of the pore space--the space between solid particles-is occupied by water at the time. Finally there is organic matter. Depending on the soil type, about three to five percent of soil is composed of organic matter.

Particle size

Particle size has much to do with a soil's drainage, tilth, and nutrient holding capacity. Although particle size seems to be uniformly categorized as small, there is a great difference is size. The difference can affect soil quality. If a particle of sand were the size of a basketball, then silt would be the size of a softball, and clay would be the size of a golf ball.

Soil type descriptions

People describe soil types in all kinds of ways such as heavy, light, sandy, clay, loam, poor, or good. Soil scientists describe soil types by the proportion of sand, silt, and clay particles present. The texture of the soil is determined by the blend of these various sized particles. By classifying soils in a particular site, you can help to determine what types of problems you might encounter when trying to grow plants. It is possible to change the texture of soils through the addition of various amendments in specific amounts. Changing composition or texture can help in providing the proper conditions needed for plant growth that might not have existed before.

More about sand, silt, and clay

Sand is the largest particle in the soil. When rubbed between the thumb and finger, it feels rough and gritty. This is because it has sharp edges. Soils with large amounts of sand are called light textured. It has little nutrient holding capacity.

Silt is a soil particle whose size is between sand and clay. These particles feel smooth and powdery. When wet it feels smooth but not sticky. If silt is rolled between the fingers, it will break up before a long ribbon is formed.

Clay is the smallest of particles. Clay is smooth when dry and sticky when wet. When clay is rubbed between thumb and finger, a long ribbon can be formed. Soils high in clay content are called heavy soils. They have a high nutrient holding capacity.

Soil for gardening indoors

When growing plants indoors in containers, soil right from the garden should not be used if you expect good results. The soil usually contains weed seeds, disease organisms, and drains poorly. If you want to use soil from the garden to illustrate how different soils might affect the growth of plants, it must be mixed with other things or amended. A suggested mix using soil is:

  • 1 part soil

  • 1 part peat

  • 1 part course sand or perlite

The amendments will help to provide the drainage and aeration needed for good plant growth. Even better indoor growing media are the artificial soils or soilless mixes. They are called artificial because they contain no soil but are made up of peat, perlite, vermiculite, and nutrients in various percentages. They have many advantages over soil. They are clean, lightweight, provide for excellent drainage, and easy to obtain. They are excellent for growing most plants indoors in containers. Soilless mixtures are available under several trade names such as Jiffy mix, Redi-earth, Pro mix, and Sunshine mix. When using soilless mixes be sure to pre-moisten them before filling your container. Also, because artificial mixes contain no soil, they don't have a great deal of nutrient holding capacity. Therefore, you will need to fertilize plants regularly to maintain adequate nutrients in the soil.

Soil activities

Students can bring in soil samples from their own gardens. These samples can be visually compared and notes made on how they differ. A soil collage can be made using the soil samples that students bring to class. These samples can be put into plastic sandwich bags and attached to a bulletin board to note visual differences.

Soils that are brought to class can be dissected. Students can physically separate and sort the samples into their components and put similar items into piles. They will be able to see differences in soils brought in from different areas of a neighborhood. Also they can work up percentages of different items against the whole.

Soils that are brought in can be separated out in to the particles that make up the soil by putting a cup of soil into a quart jar, adding water to one inch of the top, sealing the jar, shaking it vigorously, and letting it sit. The heavier particles (sand) will settle out first, followed by the lighter particles. This will result in bands or layers of various thicknesses. Soils from different areas will produce different sized bands depending on the percentages of the different particles present. With this activity the students can produce graphs, charts, and figure percentages.

Soil Mapping

The actual process of soil mapping consists of walking over the area at regular intervals and taking notes on soil differences and all related surface features such as slopes, land use, vegetation types, and other features.

A school soil map can be developed as a class project by systematically surveying and taking notes of features on the grounds. Before starting, establish a pattern or grid (divide area into units) so it can be easily transferred to paper. In addition to physical features, soil samples can be taken at regular intervals. These samples can be separated into sand, silt, and clay as was done in previous activities. Students can see if the percentage of each component changes in the area that is being surveyed.


Composting takes advantage of the natural cycle of plants living, dying, and decomposing to pass their vitality to new generations of plants. Compost, the end product, is a valuable source of nutrients for plants that also helps to improve the texture and fertility of the soil.

There are many different types of materials that can be used in compost, and each has its own good and bad points. Think of compost as the soil's diet. The diet should be balanced between materials that are strong in nitrogen and those strong in carbon, between wet and dry materials, and between acidic and basic materials. It is important that certain elements be provided. A ready-made compost is created based upon the compost maker's assumptions regarding what nutrients the soil needs and what materials are available to the compost maker. The whole composting process starts with the natural interaction of organic materials and microorganisms.

There are four basic ingredients in a compost pile:

  • Carbon, which provides the energy food for microorganisms

  • Nitrogen, which provides the protein microorganism need to break down the carbon

  • Water and oxygen, which microorganisms need in large quantities in order to do their job efficiently.

The basic compost pile consists of layers of organic matter, sprinkled with a little soil and fertilizer, kept moist and turned to introduce oxygen. The composting process can be hastened by making the size of the material added to the pile small and by turning frequently.

Composting with critters

Studying about composting in the classroom can be made more exciting by utilizing one of nature's best composters, the redworm. Redworms lend themselves well to indoor units that can be used to integrate all aspects of the curriculum. Science, math, nutrition, reading, and art can all be integrated into a worm composting unit of study. Worm bins are easy to set up and will not produce objectionable odors when managed properly.

Basic principles of worm composting is to start with a container. The container can be any size and made of any type of material. Shallow (eight to nine inches) containers are best. Be sure there are drainage holes in the bottom and aeration holes on the side. Be sure to cover these holes from the inside with fiberglass screen or old pantyhose to keep the worms in the box. Worms need bedding to live in. The best and easiest to use is old shredded newspapers. It takes about four to six pounds to fill a 2" by 2" box. Moisture is also critical. Worms need it to help them breath. Also keep in mind that a worm is about 75 to 90 percent water. Pre-moisten the bedding before introducing worms. A general rule of thumb is to use a ratio of three parts water to 1 part bedding. So , if you use four pounds of shredded newspaper, you need to add 12 pounds of water (1 pint = 1 pound).

The best worms to use are called red wigglers. These worms can handle the warm temperatures of a classroom very well and thrive. How many worms you need to start your worm composter depends on the amount of garbage you think you will generate each day.

Generally, it takes about two pounds of worms to consume about 1 pound of garbage a day. Once established, worms are heavy feeders. Worms do best at temperatures between 55 degrees F and 75 degrees F. Worms will eat a variety of vegetable waste. Meat waste should not be used in the bin. General maintenance consists of monitoring the moisture levels (don't let it get too dry), providing food, keeping it at the proper temperature, and occasionally removing the castings (worm manure) that is produced and replacing it with fresh bedding. The castings that are produced can be used in various science related projects dealing with plant nutrition. A variety of good reference manuals are available to help with class activities and worm biology.

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Home Case 1 - In Search of Green Life Case 2 - Soiled Again! Case 4 - Plantenstein Is the Suspect! Case 5 - Mysterious Parts That Surprise! Case 6 - You've Learned the Mysteries of Green Life Glossary Links Teacher's Guide Credits The Great Plant Escape Intro Glossary Links Case 1 Case 2 Case 3 Case 4 Case 5 Case 6