A science fair project on how salt affects plant growth

Written by natasha parks
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A science fair project on how salt affects plant growth
Create a salinity project that answers several different questions. (Jupiterimages/Photos.com/Getty Images)

The concentration of salt in water is called "salinity." When enough salt accumulates in the root structure of a plant, negative effects are seen in the leaves, flowers and stems and the plant's growth is altered. Salt hampers the amount of water the roots take in and the plant uses up more energy trying to access the water, as researchers at Montana State University explain.

Salt Tolerance

A salt solution is simply salt dissolved in water. Take five potted plants of the same species with a visible root structure. Water the plants with increasingly saturated solutions of salt once on the first day then again if the soil runs dry. Water one plant with pure water as a control. Observe the plants over an hour, after a day and after a week. Record the results. Look at the leaves and work out if any of the salt concentrations make them go brown or shrivel up. Find out the tolerated level of salt and the level of salt which seriously affects plant growth.

The Cut Flower Test

Try the same experiment, but use cut flowers as a comparison tool. Put small bunches of cut flowers of the same plant into tall glasses. Try to make sure each glass contains the same amount of plant matter and the flowers and stems are cut to the same lengths. Add a water-only control. If the flowers in the water-only control die quickly or change colour, you know the salt is not the main factor in the experiment. Add a range of salt solutions to the other flowers. Record your observations and any effects you see.

Additive Comparison

Dissolve salt, sugar, vinegar, sand, food dye or any other safe additive in water at a high concentration. Water a set of the same species of plant with a sample of each solution and observe what happens. Record which substances alter plant growth. Compare and contrast the results you observe. Work out which substance or additive affects plants' growth and overall condition the most and explain why you think that is. Discuss the difference between the effect salt had on the plant growth rate and the effects of the other additives.

Water Stress

Research the importance of water stress in agriculture and crop irrigation using online resources such as university websites or textbooks about agriculture. Salt-affected soils are grouped according to their content of soluble salts and sodium (termed "sodicity"). As scientists at North Dakota State University describe, high salt soils, characterised by pH values of 8.5 or less, occur in areas where groundwater moves upwards from a shallow water table close to the surface of the soil. Use your online resources to research if these soils are naturally-occurring or have been created by human interaction with the land. Write down what you find out.

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