Effects of soil salinisation
Focus
This activity provides opportunities for students to develop an understanding of the effects of increased soil salinity on both native and agricultural ecosystems. Students investigate the effects of soil salinity on seed germination and plant growth.
Science
Science and Society
6.2 Students use scientific concepts to evaluate the costs and benefits of applications of science (including agricultural and industrial practices). The module also provides links to three other core learning outcomes:
6.3 Students design and perform controlled investigations to produce believable evidence.
Materials
Teaching considerations
Due to time constraints it is most practical to use plants whose seeds germinate and grow quickly. Examples are bean or sunflower seeds, or fast-growing species native to the local area, such as acacias. (Soaking in warm water will improve germination rates of acacia seeds.) Experimentation must run over a number of weeks because it takes time for seeds to germinate and grow. In cases where seedlings are required, seeds must be prepared well in advance. Germination and growth rates vary significantly from summer to winter.
Students should be encouraged to design and conduct their own experiments using the scientific method. During the experimental planning stage students may need assistance with working out:
- all of the variables involved
- how to use controls in their experimentation
- which variables are being tested and which need to be kept constant.
A framework of questions could be provided to assist students in structuring their experiments. For example, ‘What am I going to investigate?’, ‘What do I think will happen?’, ‘What happened?’, ‘Why’ and ‘What does this mean?’.
Ensure that students label all specimens and records of germination and growth rates are taken at regular intervals.
Working Scientifically
Time: 60 minutes + 10 minutes per recording interval.
- Designing and performing experiments
- Identifying and controlling variables
- Interpreting data
- Drawing conclusions
- Using scientific report genres
The teacher explains to students that they are going to examine the effects of soil salinisation on the germination and/or growth of a variety of plant species (As it takes time to record changes, it is advisable to divide the students and allocate them one task or the other, or to do both tasks concurrently). Students predict what effects varying salt concentrations might have on plants and, in small groups, discuss how to design and conduct their own experiments to test their predictions. Discussion questions could include the following:
- What types of plants could be tested?
- How can the effects of salt on plants be tested?
- What variable is being tested and which variables need to be controlled?
- How will the information be recorded?
Students conduct the experiments they have designed and record data (appearance of plants, height of plants, number of seeds germinated etc.) over a number of weeks. At the conclusion of their experiments, students reflect on their experimental procedure and discuss areas for improvement and extension. Students review the experimental data and discuss the implications of the findings for future land management strategies.
Additional learning
Students could:
- repeat the experimentation with halophytes (salt-loving plants) compared with non-halophytes
- research the effect that salt has on plants and the reasons why most plants cannot live in salty soil.
Gathering information about student learning
Sources of information could include:
- anecdotal records from observations and interviews with students during the planning and experimentation stages, and during review of the implications
- a written report including the experimental design, data, analysis and conclusions reached.
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Last updated: 09 September 2008