Teacher s Corner Lesson Plans Helping Teachers and Students Make the Most of their Outdoor Classroom Bringing Nature to our Cities www.evergreen.ca What Kind of Garden Would Grow in Our Schoolyard? Grade level: Grade 10 and 11. Sandra McEwan Provincial curriculum links: Ontario and Pan-Canadian. Subject: Science. Keywords: garden, crops, native plants, soil composition, soil fertility, soil ph, soil texture, soil structure, soil amendments, percolation rate. Description In this investigation, students will assess the soil conditions in the schoolyard by performing soil tests for ph, nitrogen, phosphorus, potassium, composition and water percolation rate. They will use this information to make recommendations for growing specific plants. Curriculum Framework This lesson is linked directly to the learning expectations described in the Ontario Curriculum for Grades 10 and 12 science. The learning expectations are also broadly applicable to other Canadian curricula, including the Pan-Canadian Science Curriculum. A: Ontario Curriculum Grade 10 Science (SNC 2D) Strand: Biology Specific Lesson Goals: ˆ explain how soil composition and fertility can be altered in an ecosystem and identify the possible consequences of such changes. B: Grade 12 Science (SNC 4E) Strand: Gardening, Horticulture, Landscaping and Forestry Specific Lesson Goals: ˆ carry out soil tests to determine optimum conditions for the growth of plants (e.g., determine experimentally, the correct ph value of the soil, or the optimum percentage of nitrogen, phosphorus and potassium for particular plants).
2 C: Pan-Canadian Curriculum Knowledge: ˆ 331-7 describe how soil composition and fertility can be altered and how these changes could affect an ecosystem. Preparation Preparation time: Approximately 40 minutes to collect and inspect equipment, assemble soil specimen jars, print and copy student worksheets, read educator notes (provided) and review references/resources (as noted below). Length of lesson: Approximately 150 minutes for class discussions and field trip. Resources required: Student worksheets, soil sample for demonstration and LaMotte Soil Handbook. In addition, each group will need: ˆ garden trowel (or large spoon) ˆ soil testing kit (ph, nitrogen, phosphorus, potassium) ˆ large juice can with both ends cut out ˆ 500 ml plastic bottle ˆ hand lens ˆ tray (pie plate size) ˆ safety glasses Procedure Note: if you have assembled all the materials in advance, this entire exercise can be conducted outdoors, including the introductory discussion and brainstorming. 1. As a class, brainstorm and discuss the chemical and physical soil properties that affect plant growth and development. 2. Review the importance of optimum ph, the role of nitrogen, phosphorus and potassium and the significance of soil composition when establishing ideal soil conditions to grow plants. 3. Brainstorm sites on the schoolyard that students might analyze for establishing a garden (wildflowers, grasses, food crops or other kinds of plants). 4. Explain how to perform the texture test by pinching a small soil sample between the first finger and thumb. Provide a variety of soil samples for students to feel. 5. Explain how to qualitatively assess the organic content of soil by using the intensity of brown or black colour (high, medium, low). Provide contrasting soil samples for students to observe and classify.
3 6. Explain the importance and classification of soil structure. 7. Illustrate how to perform the soil ph and nutrient tests. Safety goggles must be worn during the testing. 8. Demonstrate the procedure to find the percolation rate of the soil. Work the juice can into the ground (about two centimeters). Pour a measured amount of water into the can (e.g. 500 ml using a plastic bottle), and measure the length of time it takes to soak into the soil. Repeat the procedure and average the results (L/min.). 9. For aesthetic and safety reasons, remind students to avoid digging large pits when collecting their soil sample. 10. Organize students into research teams of no more than 5 or 6 members. Assign specific tasks (e.g. group leader, equipment manager, data collector, safety officer, ph tester, texture tester, nutrient testers, percolation rate tester). 11. Supervise groups as they undertake the study, as outlined in the student worksheets. 12. Back in the classroom, provide time for the research teams to discuss and/or complete the discussion questions. Discussion and Questions These questions may be used in a discussion, or as part of a written assignment. 1. Evaluate the soil as a general (overall) medium for plant growth. Make reference to each soil test performed. 2. Describe the soil amendments that could be made to improve this soil as a medium for growing the plants you recommend for your plot. What are the possible methods for making those amendments? 3. List three or four plant species that would likely thrive in the soil without amendments. If possible, include at least one food plant. 4. What additional soil properties should be analyzed? Explain the importance of these tests when evaluating soil conditions. 5. Soil texture is determined by the size of the soil particles. Explain which soil structure would produce the greatest plant growth in your proposed garden. 6. Explain how the organic content of the soil affects plant growth. 7. Predict the effects of the following soil amendments: (a) Addition of lime. (b) Addition of mulch. (c) Addition of peat moss. (d) Addition of 7-7-7 fertilizer.
4 (e) Planting a legume plant (soybean, clover or vetch). (f) Addition of nitrogen using a nitrate salt (e.g. sodium nitrate). (g) Addition of a phosphate salt (e.g. sodium phosphate). (h) Addition of a potassium salt (e.g. potassium chloride). 8. Make a list of factors that might cause deterioration of the soil quality in your study plot, and propose an action plan to reduce or eliminate these factors. 9. What are the advantages and disadvantages of choosing only native, locally-adapted species for your garden? Student Evaluation ˆ Completion of worksheets ˆ Observation ˆ Peer and self-evaluation Enrichment and Extension Activities ˆ Determine the soil preferences of specific plants species that thrive in large numbers (e.g. patch of goldenrod; stand of cedar trees) and that obviously prefer particular locations. ˆ Investigate the effects of nutrients on plant growth by adding various minerals to the soil and observe their effects on the growth of selected plants. ˆ Test the ph of several soil samples, for example, topsoil and subsoil from a coniferous forest, an open field and a deciduous forest. Account for differences in ph values. ˆ Investigate the effect of different fertilizers (natural and synthetic) on plant growth, and on the environment ˆ Investigate how fertilizer is manufactured. ˆ Investigate the advantages and disadvantages of commonly used mulches. ˆ Investigate the idea of companion planting as a way to preserve or improve soil quality for food crops and gardens. Design an experiment to assess the effectiveness of this approach. ˆ Design and perform an investigation to determine the benefits of mulching and composting soil. ˆ Research what kinds of plants are native to your area, and compare their soil needs with those of some non-native species used in your school grounds. ˆ Research the use of companion planting and other agricultural practices used by indigenous peoples in Canada. What would be the advantages, disadvantages and feasibility of adopting these practices into modern agricultural systems?
5 Educator Notes ˆ Students should have prior knowledge of the following soil terms and facts: composition of soil (minerals, organic substances, water, air); importance of organic material; soil structure; types of soil particles (gravel, coarse sand, fine sand, silt, clay); soil profile (litter layer, peat layer, humus layer, subsoil layers, bedrock layer); soil texture, soil ph, soil nutrients (nitrogen, phosphorus, potassium); methods to improve soil quality (e.g. mulching, composting, fertilizing) and factors affecting percolation rate of soil. ˆ The quality of soil is vital for promoting optimum plant growth and development. Each plant has specific nutrient and ph requirements. The mineral and organic components give soil its chemical properties. ˆ The most important chemical property of soil is its degree of acidity. Soil ph affects plant life for three main reasons: It helps determine how active the decomposers will be. It helps determine the availability of the nutrients. Some nutrients will only dissolve and be available to plants at a certain ph. It helps determine whether or not nutrients can enter the plant through the cell membranes of the root hairs. ˆ Nitrogen, phosphorus and potassium are classified as macronutrients as they are needed in large amounts by most plants. ˆ Nitrogen helps a plant produce above-ground growth. It gives plants a rich, green colour. It is used by plants to make proteins and healthy seeds and fruits. ˆ Phosphorus plays an important role in energy storage and transfer in all cells. It also helps plants develop hardy growth, good seeds and better roots. ˆ Potassium produces vigorous plant growth. It encourages root development and plays a role in photosynthesis. ˆ Soil structure refers to the size of the soil aggregates (the arrangement of individual particles into larger units). It is classified as either: Poor Structure - aggregates are too small (results in poor drainage and low absorption) or too large (not good for seed germination). Good Structure - aggregates are 2 to 5 mm wide (allows good drainage and aeration). ˆ The importance of soil structure lies in the size and extent of the pore system between the structural units. Because clay particles stick firmly together, even when wet, the presence of clay tends to give strength or stability to soil aggregates. Sand particles do not stick together or cohere. Generally speaking, soils containing a lot of clay are stable and do not collapse when wet, although they will readily compact under applied weight. Soils containing a lot of silt or sand are unstable and readily collapse when water logged.
6 ˆ The percolation rate of a soil depends on many properties of soil. Among them are: pore space, particle size, looseness or compactness of the soil, water content of the soil, vegetation cover (including roots) and the number of earthworm burrows. ˆ The main components of soil are summarized in the chart below: Component Appearance Texture Smell Coarse Sand Fine Sand Clay Peat Humus Particles with rough edges; clear, white, pink and black are common colours. Same as above, but smaller. No separate particles can be seen; usually light brown in colour. Pieces of dead plants, including pieces of wood; brown in colour. Black mass; no substances can be identified. Coarse and gritty feel. Not quite so coarse and gritty. Smooth and slippery feel. Varies, but usually rough. Smoother than peat. No odour. No odour. No odour. Slight odour of decay. Major odour of decay. ˆ Assemble sample jars of the above soil components for students to examine, feel and smell prior to the field study. ˆ Obtain copies of LaMotte Soil Handbook produced by LaMotte Chemical Products Company. It is normally included in the LaMotte Soil Testing Kits. The handbook provides lists of relative nitrogen, phosphorus and potassium requirements and preferred ph ranges for common farm and garden plants. ˆ Locate soil testing kits for measuring ph, nitrogen, phosphorus, and potassium. Kits can be purchased from science supply companies (e.g. Boreal Laboratory Limited). ˆ Familiarize the students with the chemical soil testing procedures prior to going outdoors. ˆ Scout out potential garden sites in the schoolyard for students to investigate the soil quality. Possible sites include a sunny, vegetated, loosely compacted area of the fence line, in a lawn away from high traffic areas, near the school entrance, adjacent to an existing garden, or in the vicinity of small trees/shrubs. ˆ Ideally, the students should complete all soil tests at the study site. If this is not possible, collect at least two trowels full of soil from each site on the same day the class will be completing the tests.
7 ˆ If the lawn has been recently fertilized or if new sod has been laid, the nutrient tests will not reflect the natural levels in the soil. ˆ It is recommended that this investigation be conducted in the early fall or late spring, and on a day when it has not rained in the previous two or three days. ˆ SAFETY NOTE: Consult your school board s policy regarding safety precautions for outdoor excursions and plan your trip accordingly. Be aware of any students with allergies to insect bites and plants and ensure they carry the required medications. Students should wash their hands after handling soil, plants and equipment. Encourage students to wear sunscreen and appropriate clothing (e.g. hat, long-sleeved shirt) to minimize the damaging effects of sun exposure. References ˆ Federation of Ontario Naturalists (FON) and Soil and Water Conservation Society (SWCS), Ontario Chapter. Don t Treat Soil Like Dirt Soil Conservation Kit. Toronto: FON. 1995. ˆ LaMotte Chemical Products Company. LaMotte Soil Handbook. Chestertown: LaMotte Chemical Products Co. 1985. ˆ Ontario Ministry of Agriculture and Food. Origin, Classification and Use of Ontario Soils. Publication 51. Guelph: Ontario Agricultural College. No date. ˆ Numerous soil fact sheets and booklets can be obtained from: Agriculture Canada; Ontario Ministry of Agriculture and Food and Water Conservation Society (SWCS). Worksheets Student Worksheet Date: Group Members: Site Location: In this investigation, you will perform various chemical and physical soil tests to evaluate the soil quality and make recommendations about the kinds of garden plants, farm plants, wildflowers, grasses, cultivated plants and food crops that would thrive in your school grounds, and how to support their optimum growth. 1. Select a 1m x 1m area of the schoolyard to develop a wildflower garden or food garden. Describe the location and soil cover. 2. Use the garden trowel to collect a small soil sample at a depth of 5cm. Avoid transferring any surface litter, grass or rubbish to the pan.
8 3. Perform the following tests on the soil sample: texture, structure, organic content, smell, ph, nitrogen, phosphorous and potassium. Complete the water percolation rate test. Record the results of your test in a table. Safety goggles must be worn during the chemical testing. 4. Attempt to classify the soil particles in the samples. 5. Describe the water-holding capacity of the soil. 6. Return the soil sample. Wash your hands after completing the investigation. 7. Using the LaMotte Soil Handbook, and other resources provided by your teacher, make a list of the plants you d recommend to be planted in your plot, based on your study results. For each plant, record its preferred soil type, ph range and nutrient requirements. Your list should include at least one of each of the following kinds of plants. (a) Wildflowers (b) Food plants (c) Non-food garden plants (e.g., shrubs or ornamental plants) (d) grasses