A-Salt on salinity

Salinity is a huge environmental problem in Australia. Dryland salinity, which is rising salt that damages soil, plants and buildings, is hard to comprehend and harder still to stop. Approximately 5.7 million hectares are at risk of, or affected by, dryland salinity. In 50 years, it is estimated this area may increase to more than 17 million hectares.

You will need

  • 35 wheat seeds
  • Cling film
  • Five small potting containers (polystyrene cups work well, remember to add a drain hole)
  • Potting mix
  • Tap water
  • Salt
  • Five one litre (or bigger) bottles
  • Marking pen
  • Results record sheet (download from link below)

What to do

Sow your seeds

  1. Label each of the containers with a solution number from Solution 1 to Solution 5.
    cartoon of person performing the experiment watering the plants.
  2. Fill each container with potting mix.
  3. Place seven evenly spaced seeds into each container. Don't use the seeds that are cracked.
  4. Wet the soil in each container with tap water, cover with cling film and place in a warm sunny location.
  5. Grow the seedlings for about one week, until the second leaf is emerging.

Make your salt solutions

  1. Make the salt water solutions in five clean, empty bottles.
  2. Label each of your containers Solution 1, Solution 2 etc.
  3. Make your solutions according to the table below.
  4. When the second leaf on each plant is about 50 millimetres long, start watering each container with the corresponding salt solution.
  5. Measure and record the length of the second leaf before you put any solution on the plant, and then measure the same leaf each day after that. Use this chart [pdf · 1mb] to help you record you measurements.
Amount of salt in teaspoons Amount of water

Solution 1 (tap water)

0 (0 grams)

1 Litre

Solution 2

½ teaspoon (3 grams)

1 Litre

Solution 3

1 level teaspoon (6 grams)

1 Litre

Solution 4

2½ level teaspoons (15grams)

1 Litre

Solution 5

5 level teaspoons (30 grams)

1 Litre

Helpful Hints

  • If you miss the second leaf you can use the third leaf as your test leaf. Don't use the first leaf as it only grows to approx. 100 millimetres.
  • If you use table salt you will find that there is a residue that does not dissolve it is the compound added to keep the salt dry.
  • Plant seven seeds and pull out the worst two, which are the two that emerge last, or not at all, so you are left with five good seedlings per container.

What's happening

In this experiment, some plants were grown with normal water. These plants should grow normally. Wheat plants grow from the base like other grasses. New cells are formed at the base of the plant and this pushes the tip along. The second leaf should grow about 30 millimetres per day, and reach a final length of about 150 millimetres. When you add salt water to the plant the growth rate of the leaves should decrease.

To see the results of the different solutions of salt water, make a graph that shows how fast the leaf grows in millimetres per day, and how badly the salt affects this.

  • Solution 1 should have no adverse effect on the plant and growth should be normal (30 millimetres per day)
  • Solution 2 will have only a small effect on the wheat seeds.
  • Solution 3 should have a bigger effect.
  • Solution 4 will cause growth to slow dramatically and nearly stop.
  • Solution 5 will kill the plants.

Plants absorb water from the soil through their roots by osmosis.  Salinity is bad for osmosis and can even make the plant lose water back into the soil, making them dry and wilted.

The problem of salinity in Australia

landscape effected by salinity with trees and scrubs dead and dryNative Australian vegetation has evolved to be salt-tolerant. But when European farming arrived and replaced the natives with crop and pasture plants that have shorter roots and need less water, the inevitable happened.

With every fall of rain, unused water leaks to the water table, raising it and bringing the salt up with it. That process continues today, and the volumes of water and salt are vast.

Under the soils of the Western Australian wheat belt and some parts of eastern Australia the salt store is so immense, and the movement of sub-surface water so slow, that restoration to fertility of salt-affected land will take generations. Some areas may never recover.

Our research shows that, even if we replant up to 80 per cent of the native vegetation, some cleared catchments would not see recovery within normal human timescales.

It is a tragic irony that the felling of many billions of trees to make room for the farming that let this nation prosper has caused, in just 150 years, our worst environmental crisis, and destroyed a natural balance that had existed for millenia.

Salinity research and CSIRO

The great challenge in catchment science is the ability to predict the changes in water and salt levels in large river basins. CSIRO’s Surface Water and Groundwater Interactions team aims to increase our ability to make these predictions, both in terms of water quality and quantity.

The team explores the implications of different pressures on river water, such as upland land use change, climate change, salinity, and groundwater balance. We assess these changes and their impacts on water consumption and the environment.

The Surface Water and Groundwater Interactions team focusses on developing integrated models of regional catchment hydrology, which can be used to develop water resource planning and water operations. This modelling capacity and hydrological knowledge are being used to support the National Water Initiative.

The team is also exploring the ecological consequences of environmental water allocations. These are in conjunction with regional assessments of salt and groundwater nutrient pollution and similar research on surface transport of sediment and nutrients.


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