What happens when you water plants with salt water of different strengths? You prepare several salt concentrations and water identical plants with each one daily. You observe and record the growth over about 15 days.
The highest concentrations (6 and 8 ounces of salt) caused the most damage. Plants watered with plain water showed no harmful effects. The salt added to the soil built up over time. This increasing salt concentration harmed growth from the roots up.
Hypothesis
The hypothesis is that the largest concentration of salt will harm the plants the most.
Osmosis moves water through a barrier from more water to less. You water identical plants each day with different amounts of salt mixed in. Salt dissolved in soil water means less free water on the outside of root barriers. Plants watered with plain water showed no harmful effects because their roots had plenty of free water to pull inward.
Salt added to water can hurt plants, and more salt means more harm. When plants received plain water, they showed no harmful effects. The highest concentrations — six and eight ounces of salt — caused the most damage as the salt built up in the soil over time.
Control variables are the things you keep the same so your test is fair. In this experiment, you use identical plants and water them each day. The only thing that changes is the salt amount. Keeping everything else the same lets you know the salt caused the damage, not something else.
Method & Materials
You will purchase plants, prepare the water with salt concentrations, and water the plants each day with the different concentrations of salt.
The results showed that the 8 and 6 ounce salt water concentrations harmed the plant growth the most. The water did not harm the growth and showed no visual effects on the plants.
Why do this project?
This science project is interesting because it shows how salt water can affect the growth of plants, which is something that is not often considered.
Also Consider
Variations to consider include testing the effect of man-made salt water and ocean water on plants, or testing the effect of different types of salt on plant growth.
Full project details
Additional information and source material for this project are available below.
