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Effect of water hardness on seed germinationFeatured science projectScience project video


This science fair project was conducted to ascertain if the hardness of water used on seeds will affect their germination. The science project experiment involved blackeyed Susan seeds that were made to germinate by watering with hard water, tap water and soft water.


Watering plants with soft water will help seeds germinate more quickly

Scientific Terms

Germinate, photosynthesis, divalent salt, water hardness, water softeners, ion exchange


Water and plant growth

Seeds need water, oxygen and the correct temperature before they can start to germinate and grow. After the seeds have germinated, they will also require light and carbon dioxide for photosynthesis. Plants will normally die if they are deprived of water and oxygen. The amount of water supplied to the plant or seed is also important. Too much water will cause the roots to be covered with water and deprive them of oxygen. This can cause the root to rot and kill the plant.

The water that we obtain from the tap or other sources is normally not pure. There will be some minerals or divalent salts in the water. The most common is calcium, magnesium and iron. The amount of calcium and magnesium present in the water will determine the hardness of the water.

The hardness of the water can be reduced by using water softeners. Water softeners help to reduce the amount of calcium and magnesium that is dissolved in the water. Sodium carbonate is an example of a water softener that is commonly used. Water softening takes place by ion exchange where the sodium ions and calcium, or magnesium ions, will "exchange" places.

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Complexity level:
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Time required:
1 day to prepare, 5 days for the science project experiment
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Safety concerns:

Basic safety requirements