Science Fair Ideas for Compost

• Building a compost pile might be the first part of a science project. Paul Viant/Stockbyte/Getty Images

  Many students are turning to science projects that reflect a trend in preserving natural resources and reducing pollution. Composting helps eliminate some of the trash people generate by changing plant matter into plant food, and it does so without the fossil fuels used to produce synthetic fertilizers. Compost creates healthy plants by moderating water retention and improving soil structure. These characteristics and more can be explored as a science fair project.

Plants Grown With and Without Compost

• Collect 10 identical pots, one bag of potting soil with no fertilizer added, and one bag of compost. Fill five of the pots with bagged soil and five with bagged soil mixed with the manufacturer's recommended amount of compost. Plant a bean seed in each of the pots. Thoroughly water, cover loosely with plastic wrap, and check on the plants every day. Once they begin to poke through the soil, remove the plastic wrap and place the pots in the sunlight or under grow lamps. Make sure that each plant receives the same amount of light. Determine a watering schedule and water each plant on schedule with the same amount of water for each plant. Record the plants' growth, count their leaves, and examine their overall appearance; keep this data over the course of three weeks.

Hot Piles Versus Cold

• Assemble two, 4-by-4 foot piles of various plant-based materials. Grass clippings, straw, leaves, and table scraps work well. Try to use the same amount of each material in each pile. In one of the piles randomly scatter the plant matter: this is your cold pile. In the other layer the "browns" (straw, dry leaves) with the "greens" (kitchen scraps, fresh grass clippings) alternating each layer; this is your hot pile. Lightly dampen both piles. Every three days mix your hot pile with a garden fork. Water it as needed. The pile should be damp like a wrung out sponge. Leave your cold pile untouched. Every three days or so for at least four weeks, compare the amount of decomposition that occurs. The more decomposed the item is the less it will look like its original form. Maintain a notebook in which you record your observations.

Water Retention of Compost-Amended Soil

• Line 10 small mesh baskets, each with one coffee filter. Put each of these on top of a cup, beaker or jar. Fill five of the lined baskets with garden soil; this is your control group. Fill five with garden soil amended with compost; this is your experimental group. Don't over-fill; make sure there is a 1 inch difference between the rim of the basket and the top of the soil. Carefully pour one cup of water over a mesh basket from each group. After 15 minutes remove the soil and water mixture and measure and record the amount of water left in each container. Repeat this procedure with the remaining control and experimental groups. Find the average for each.