How important is soil?

Preparation

Collect the following materials required by the investigation worksheet: sets of plants in seedling trays (one plant type per group), salt and water, a measuring jug, kitchen spoon measuring set, stirrers, mini plastic plant pots, compost, measuring cup (1/3 cup)

Curriculum links

• Australian Curriculum: ACSSU094, ACSIS232, ACSIS103, ACSIS104, ACSIS107, ACSIS221, ACSIS110
• NSW Curriculum: ST3-4LW-S, ST3-1WS-S, ST3-2DP-T
• Vic. Curriculum: VCSSU075, VCSIS082, VCSIS083, VCSIS083, VCSIS084, VCSIS085, VCSIS086, VCSIS088
• WA Curriculum: ACSSU094, ACSIS232, ACSIS103, ACSIS104, ACSIS107, ACSIS221, ACSIS110

Suggested teaching strategies

• Construct a vocabulary wall to collect and display vocabulary throughout the unit. Alternatively, students could keep a personal dictionary of terms at the back of their notebook.
• Prior to commencing the digital lesson, students can participate in a fishbowl discussion sharing their opinions about the importance of soil.

Introduction

Display the digital lesson on your smartboard to discuss the importance of soil.

The student summary and worksheet pages should be used together.

Development

Provide students with the summary and worksheet to complete.

The purpose of the investigation worksheet is to explore the effect of soil salinity on plant life. The students need to understand that in any experiment a control or control group is needed. The control is the object, material or substance that nothing is done to; it remains the same (unchanged) and serves as the standard (or blank state) that the other objects, materials or substances are compared to.

The ‘Before you begin’ questions can be discussed within groups but may need to be standardised before the investigation starts.

Every group can explore a different plant type in the experiment. If this is the case, the class as a whole can also determine which plant is the most/least salt tolerant. For this, the concentrations of the salt solutions must be the same among all groups. These can be made by using a standard kitchen spoon measuring set and adding 1/4 teaspoon, 1/2 teaspoon, 1 teaspoon and 1 tablespoon of salt to cups of 250 mL of water. An equal amount of plain water should be used for the control.

To ensure a fair test, the plants should receive equal amounts of watering solution. Transfer the seedlings to small flower pots and add equal quantities of compost to each for stability. All test plants must be located in the same place.

Differentiation

• If students require additional support, jointly conduct the investigation and complete the worksheet in small groups or as a whole class.
• The rising watertable is a problem for farmers across Australia. As an extension to this lesson, ask students to come up with ideas that could decrease salinity in a farming region. They may also research the current methods that exist.

Conclusion

If different plant types were used by groups, share results as a class to discuss which plants were most/least affected by salinity.

Discuss how any discoveries made could be useful knowledge for farmers.

Assessment

Worksheet answers
1. (a) Weathered rock particles and living and decayed organic matter (b) stability, water, nutrients 2. (a) By the type of rock it comes from and the size of rock particles in it. (b) How much air and water it can hold; if it is acidic or alkaline. 3. Plants grow better in fertilised soil but fertiliser can be washed into waterways causing an algal bloom. 4. Teacher check: Groundwater – the water present underground; Watertable – how far the level of the underground water is below the surface. 5. (a) They grow deep into the soil, taking up lots of groundwater, keeping the groundwater level from rising. (b) They do not grow very deep and they use much less underground water, especially when watered from above. 6. (a) Salt is present in the ground and dissolves in the groundwater as the level of the watertable rises. (b) Salt makes it more difficult for roots to take up water. This causes plants to dehydrate. Salt that does get into the plant can not get out again and damages the cells of the plant. (c) Most plants can not tolerate a high level of salt and so will not be able to grow and survive in soil with a very high salt content.

Investigation worksheet answers
Students will discover that as the concentration of salt increases, the growth of the plant diminishes. In their evaluations, students could consider altering the concentration levels if they were to repeat the investigation. If all plants die, then even the lowest concentration was too much and more dilute solutions must be made. If all plants thrive, then more concentrated solutions must be made.