Science Project: How Does Salt Affect Seed Germination?

Why this is an Important Project

Although this science project is very easy and uses simple materials, it examines a very important problem, the build-up of salt deposits in soil which prevents germination of seeds. When she was in 7th grade, my daughter did this science project and won our regional fair, much to our surprise. We think it was because her project design was original (developed with her dad, who is a biologist), simple, and because her project dealt with a real-life problem.

Variation using Plants

You can do a variation on this project by watering plants with water with different concentrations of salt to see how salt water affects the growth of plants. As the co-ordinator of an elementary science fair, I've seen students do lots of plant watering experiments using different kinds of water, but I've never seen a salt experiment.

How Salt Gets Into the Soil

This would be an excellent additional research topic for your child. They can look up how farming practices using irrigation and manure cause salt to be deposited into the soil. You can also do an experiment letting a container of salt water evaporate so that your child can see how salt remains when water evaporates.

One Thing We Learned

Our first version of the experiment had none of the seeds germinating! So we had to re-do the experiment with less salt in the water. If you have time, it helps to do a pre-test of an experiment. However, scientists are always honest. If your experiment doesn't work out but you did everything you said you would do, you should still publish your results exactly. What you can put in your conclusion is how you would alter the experiment next time. We had time to re-do our experimental design and try again, which is exactly what my husband does when his experiments don't work the first time!

Materials

• Plastic Ziplock Bags
• Coffee Filters
• Seeds: You can use any sort of seed, but raddish seeds are small and inexpensive.
• Water
• Salt 

Junior High Research Plan

This is the research plan my daughter used for her Junior High Project. For elementary students, you should have them put what they do into their own words. 

Problem: How much teaspoons or portions of teaspoons, of salt dissolved in a cup of water can be withstood by a 100 germinating radish seeds if 1 tablespoon of the salt water in the cup is added at a time in a Ziplock Bag with a coffee filter to hold the water?

Safety: You need goggles for the salt water splashing in your eyes, and gloves so you do not transfer bacteria to the seeds.

Hypothesis: The more salt in the water, the fewer seeds will germinate. The radish seeds will not germinate at all in a solution with more than 3 teaspoons of salt in 8 oz of water.

Materials: 10 Ziplock Bags, 1000 radish seeds, 10 coffee filters, tap water, distilled water, table salt , teaspoon, 10 cups, 8 oz. measuring cup (tap water is the control).

Procedure:

1. Take ten separate cups. Label them A through J. Fill them as follows:

• Solution A: 8 oz. tap water
• Solution B: 8 oz distilled water
• Solution C: 8 oz distilled water with ½ teaspoon of table salt. Stir to dissolve salt.
• Solution D: 8 oz. distilled water with 1 teaspoon of table salt. Stir to dissolve salt.
• Solution E. 8 oz. distilled water with 1 ½ teaspoons of table salt. Stir to dissolve salt.
• Solution F. 8 oz distilled water with 2 teaspoons of table salt. Stir to dissolve.
• Solution G. 8 oz. distilled water with 2 ½ teaspoons of table salt. Stir to dissolve.
• Solution H. 8 oz. distilled water with 3 teaspoons of table salt. Stir to dissolve.
• Solution I: 8 oz. distilled water with 3 ½ teaspoons of table salt. Stir to dissolve.
• Solution J: 8 oz. distilled water with 4 teaspoons of table salt. Stir to dissolve.

2. Place the 10 Ziplock Bags down on the counter at room temperature. Label the top and bottom of each plate with the letter of the solution to be used in each one (A through J).

3. Unzip the bags and put a coffee filter in each one.

4.. Pour one tablespoon of each solution onto the filter in the bag with the same label, making sure it soaks the whole coffee filter.

5. Divide the 1000 seeds into groups of 100. Put 100 seeds on the filter of each Bag. Make sure the seeds are scattered evenly over the filter.

6. Zip up the Bags. Place all 10 dishes at room temperature out of direct sunlight (seeds don't need light to germinate and light can cause fungus to grow).

7. Observe the dishes daily and record number of seeds that have germinated in each dish and any other changes in the seeds.

8. Record results in journal.

Abstract of Experiment and Results

The problem was to determine the effect of salt water on germinating radish seeds, and also to determine if there was a maximum concentration that could be tolerated.

To do this, coffee filters were wet with 1 tablespoon of salt water from cups that increased in concentration by 1/2 teaspoon of salt in each cup of 8 oz. of water. The filters were then placed in the plastic bags. The 50 seeds were then placed on top of the coffee filters, inside the bag. The seeds that germinated were counted and charted. Tap and distilled water without salt were used as controls.

The results were that the germination was 100% with the controls, tap and distilled water. On the groups exposed to salt water the germination decreased as the salt concentration increased, and no germination occurred at amounts of 1.5 tsp. of salt or higher. This supported the hypothesis, which was, "The more salt in the water, the fewer seeds will germinate."

This information could help gardeners and farmers to know when saline reaches dangerous levels for radish seeds.