- Observe the effects of mulch on conserving water.
- Create a natural form of weed control.
Pa. Standards Addressed Doing the Activity
- Teaching Methods Assessment and Evaluation
- Background Extensions
- Getting Ready Resources
Pa. Environment & Ecology Standards Addressed
- 4.2.7. Renewable and Nonrenewable Resources
A. Know that raw materials come from natural resources.
- 4.4.7. Agriculture and Society
B. Explain agricultural systems’ use of natural and human resources.
- 4.6.7 Ecosystems and their Interactions
A. Explain the flows of energy and matter from organism to organism within an ecosystem.
- 4.8.7 Humans and the Environment
B. Explain how human activities may affect local, regional and national environments.
Other PA Standards Addressed
- Science & Technology
- Reading, Writing, Speaking and Listening
Teaching Methods Incorporated
Hands-on, Inquiry, Writing, Data Collection, Experiment, Small Group, Discussion, Investigation, Problem-solving, Analyzing, Presentation
- Newspaper (to act as mulch) – 4 double sheets per group
- 1 pair of scissors for each group
- Hose or watering can
- Soil Thermometer
- 2 soil sample containers (medicine cups, film canisters, etc.) per group
Plants all have the same needs whether they are intentionally planted or grow somewhere on their own. They all need water, sunlight, adequate space and nutrients.
Many gardeners use mulch around the base of their plants to keep unwanted plants (weeds) from growing. Mulch is simply a surface covering that is applied to garden soil. There are many different materials that can be used for mulch including wood chips, compost, grass clippings, plastic or newspaper. Using mulch is beneficial for many reasons:
- Keeps weeds down. Mulch won’t keep every weed from coming up, however it will control enough of them so that weeding is not as labor intensive.
- Conserves soil moisture. Mulch keeps water from evaporating from the soil surface. It can make the most of a good rain, holding water that would otherwise run off and letting it trickle into the soil.
- Moderates Temperature. Mulch keeps soil cooler in summer and warmer in winter. The temperature of mulched soil is more constant than that of unmulched soil.
- Attracts earthworms. Earthworms work hard to cultivate soil, but if ther soil is too hot they will stay in the subsoil to keep cool. A soil cooled by mulch will bring them closer to the surface.
- Prevents soil erosion. Rainfall will not wash soil away if the surface has been mulched, even on a steep slope.
- Improves soil structure. Mulches consisting of organic matter decompose and gradually work their way into the soil, thereby improving its structure.
Although mulch has many benefits, it also has certain drawbacks:
- Keeps the soil too cool or moist. This is especially true in early spring when young plants are beginning to grow and need warmer, dryer soil.
- Causes plants to rot. Moisture sensitive plants may be particularly susceptible to rot or fungus growth if mulched.
- Attracts pests. Mice and other rodents often burrow in mulch, either to nest or look for seeds, and they can nibble on plants while they are there. Mulch can also be a hiding place for slugs and snails, which can do serious damage.
Pick areas in the garden where each group will work. Each group will need an area for their mulch mat (12” x 14”) and another area next to it that is the same size for a control plot. ou will want to put markers at the sites so that the students can locate their areas each time they visit.
Doing the Activity
In the classroom
- Ask the student to tell you what plants need to survive. Remind them that weeds have those same needs. Ask students how to keep weeds out of a garden (pulling the weeds, spraying weed killer, mulching, etc.) and discuss the pros and cons of each idea. Explain that the best way to get rid of weeds is to prevent them from growing in the first place. Placing mulch around plants is a good preventative for weed control and it also has other benefits, as well as drawbacks, that the students will discover.
- Tell the students that they will be doing an experiment to see if mulching is beneficial for controlling weeds. Divide the students into small groups. Explain that each group will have an assigned area in the garden where they will be placing mulch around a plant. Next to the mulched area will be an area that has a plant that will not be mulched. This is called a control plot. Each group’s assignment is to monitor the mulched area and the control plot to identify the benefits and drawbacks of mulching.
- Give each group 4 sheets of newspaper folded together and a pair of scissors. Explain that the newspaper will be used as mulch. Show the groups how to cut a slit in the side of the sheets of newspaper that will enable them to slide it around a plant stem. Have the students cut slits in their newspaper. Give each student a “Covering Ground” worksheet or supply them with information you would like them to collect in a journal.
In the garden
- Have the groups take the sheets of newspaper to the garden. Assign each group to a space that had previously been marked. They will decide where to place the mulched area and which area will be the control plot.
- Have students place the newspaper mulch around a plant in the mulched area. The paper can then be anchored down by sprinkling it with water and then putting a thin layer of soil over it. Tell the students that eventually the newspaper will break down and become part of the soil. Now have the students to choose a plant in the control plot that they will observe.
- Now that their plots are set up and ready for monitoring ask them what other benefits/drawbacks mulch would have for a plant. Discuss their ideas.
- Have them draw a map of their site on the “Covering Ground” worksheet or in their journals.
- Every two or three days, have the students check their plots and answer the questions on the worksheet.
- Working in their groups, have the students compare the data collected over the given time period and determine the benefits and drawbacks of using mulch. Have them present their findings to the rest of the class.
- Observation of students.
- Accuracy and completeness of the “Covering Ground” worksheet or journal entries.
- Student presentations on their experiment findings.
Have students experiment with different mulch materials to see which one has the most benefits and least drawbacks.
- Texas Agricultural Extension Service, Junior Master Gardener, 1999
- ISBN# 0-9672990-1-2
- Damrosch, Barbara, The Garden Primer, Workman Publishing Company, New York, 1988