Effect of Salinity on Beans

Find out what level of soil salinity can be tolerated by beans. You will need:

Bean seeds or seedlings.

25 kg potting mix

Slow release fertilizer

25 pots (6 inch diameter)

Labels for the pots

Table Salt

Water (preferably rainwater)

1. Plant the seeds or seedlings into the 25 pots filled with potting mix.

2. Add a teaspoon of fertilizer to each pot.

3. Divide the pots into five groups of five replicates each. Each group of five pots will be subjected to a separate treatment The five treatments are:

plain water

0.6 g salt per litre of water

1.8 g salt per litre of water

3.5 g salt per litre of water

7.0 g salt per litre of water

Stir the water and salt until all of the salt has dissolved.

Work out the molarity of each solution of salt.

4. Label each pot with the treatment, your name (or the name of your group) and the date you began the experiment.

5. Water the pots with the appropriate salt solution as they require it. Make sure the soil does not dry out, or get too wet and soggy.

6. When the plants in the "plain water" treatment are about 20 cm high, stop the experiment.

6a.Count the number of living and dead plants.

6b. Measure the height of the plants.

6c. Cut the plants at the base and dry them in paper bags. When the plants have dried, weigh them and record their weights.

7. Calculate the average the weight and height of the plants for each treatment and present your data on three separate graphs (survival, average weight, average height).

At what level of salinity could you detect a decrease in plant performance?

Find out what the salinity of tap water is over summer, by contacting your local water board, or by measuring it yourself. Is tap water safe to use for watering beans?

Write your experiment up as a report, showing what you did and what you found.