"Leaf" It in Your Yard Background Information

Related Topics: vermicomposting, food chains, food webs, energy pyramid, decomposition, nitrogen cycle, change, ecosystem, matter, energy

Ohio Academic Standards Alignment: Click here to view content standards alignment to Science for Ohio by grade level.

Background Information:

• Composting is the managed decomposition of plant-based organic matter such as leaves, grass clippings, food, and manure (from plant-eating animals such as horses or cows) into rich soil that can be used as fertilizer.  This organic matter is unstable, in that decomposition occurs in a matter of hours, days, or weeks.  More stable matter such as plastics and metals may take years or even centuries to decompose/break down!  Composting can occur as elaborately as in a commercially sold composting container or as simply as a pile of leaves in the corner of a yard.
• Starting a compost pile is easy to do in the fall.  After the leaves have fallen, rake them together in your composting area.  Mix some soil, humus, or cow/horse manure into the leaf litter to introduce organisms (fungi and bacteria) that will cycle your compost back to the air, water, and soil.  Consumers such as worms, pillbugs, and millipedes will also enter your pile from the surrounding soil.
• Consumers.  The consumers in a compost pile, like all living things, need 1) energy from food to grow and reproduce, 2) air (oxygen), 3) moisture, and 4) space.  The compost is their energy source.  With adequate air and water, these consumers will grow and reproduce.  More consumers mean faster decomposition.
• Food Web. The Food Web of the Compost Pile shows the ways that energy is passed through a compost pile.
• Moisture.  Keep your compost pile uniformly moist, but not drenched.  The best analogy for moisture is to compare ideal moisture to that of a wrung-out sponge.  Organisms that will live in the compost pile and decompose the leaf matter prefer moist and shaded rather than sunny and dry.
• Maintenance.  For a highly efficient compost pile (one that creates humus in three to six months), turn your pile every two weeks in order to balance air, moisture, and food throughout the pile.  Don't worry if you aren't passionate about your composting.  A pile totally ignored will still decompose, but may take ten months to two years to do so.  Add leaves, grass, and plant-based food to your pile anytime, but be sure to bury food in the pile.  Burying the food prevents unwanted critters from bees to raccoons from visiting your pile.  It also speeds decomposition by surrounding food with organisms that will decompose it in the soil.
• Cautions. Composting should not include animal-based organic matter such as meats, bones, and dog/cat manure.  Bacteria harmful to humans, such as e.coli, are found in these animal products and can cycle into the compost and consequently into the foods grown from compost that we like to eat.
• Misconception(s).
• Misconception: Decomposition can only happen in a compost pile.  Fact:  Decomposition occurs all around us everyday.  If it didn't, we would literally be swimming in dinosaurs and other organisms that have died since the beginning of time.  A compost pile merely accelerates the decomposition process.
• Misconception: Compost piles stink.  Fact:  A compost pile has a pleasant "earthy" odor unless an excessive amount of inappropriate matter is put in the pile (i.e., meats) or unless the pile is flooded with water and not turned to circulate air for a period of weeks (i.e., anaerobic decomposition).  In the case of meat, removing the meat will solve the problem.  In the case of overwatering, turn more frequently and mix in dry material.
• Expected Results. Students should conclude from their research that a productive pile is one that is begun in layers (i.e., grass, leaves, soil) and maintained with adequate moisture and air through water and turning of the pile.  A compost pile started in October/November and maintained once or twice a month throughout the year will be mostly if not totally decomposed by the end of the school year.