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What Is The Effect Of Saltwater In Plant’s Growth?

What Is The Effect Of Saltwater In Plant's Growth?

Introduction: (Initial Observation)

You may have noticed there are almost no plants near oceans and salt water lakes while there are many plants near fresh water lakes and rivers. Is there any relation between salt and growth of plants?Is it possible that salt somehow stops the growth of plants?

Is it possible that salt somehow stops the growth of plants?

In this project you will investigate to find out if too much salt in soil can kill a plant or stop plant growth.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Information Gathering:

Find out about plants and what they need to grow. Read books, magazines or ask professionals who might know in order to learn about plant growth. Also study about salt and its uses. Keep track of where you got your information from.
Following are samples of information you may find:

Plants are essential to life. Not only they remove carbon dioxide from air and supply oxygen to the air, they also act as the base of many food pyramids.

How much oxygen do plants produce? Why do some plants grow more quickly than others? Why won’t some plants grow at all in Saskatchewan? If using fertilizers helps plants grow, will using more fertilizers help them even more? How does saline soil inhibit plant growth?

These are some of the questions which can be considered during this unit. Encourage your students to go beyond the information in the resources and the bounds of the classroom walls to find out about plant growth, and the importance of plants to our lives.

What Do Plants Need to Grow?

Just like humans, seeds have important, basic needs that must be met if they are to thrive and grow:

  1. Water-Water is the first step to a seed’s waking up. When a seed takes in water, its outer coat splits. Then the baby plant, called an embryo, can get the oxygen it needs from the soil. Plants always need water, which carries important nutrients from the soil to the plant.
  2. The Right Temperature-Seeds wait for just the right weather to leave their coats behind and begin to grow. Some seeds, like peppers and tomatoes, require warm temperatures to germinate, while others, like lettuces, need cooler temperatures.
  3. Soil with Room to Grow-The root is the first thing to emerge from the seed. When the young shoot begins to grow, the seed has become a seedling, nourished in this earliest stage by food that was stored inside the seed. As roots grow, they allow a plant to absorb water and nutrients. They also anchor plants in the soil. To help them get nutrients and grow, plants need healthy soil which is well aerated; that is, loose enough for air to move though it.
  4. Sunlight and Air-When the seedling’s first real leaves come through the soil, the plant switches to making its own food. Using sunlight and nutrients from the soil in a process called photosynthesis, the leaves of the plant change energy from the sun into food so it can grow. Plant leaves also need to breathe air to help with photosynthesis.

With the help of water, sunlight, and healthy soil, a little, dormant seed has everything it needs to transform itself into a strong, healthy plant. Nature’s way of providing us with delicious, nutritious food truly seems like a miracle.

These are some uses of salt:

Groceries spray vegetables by water so the vegetables will stay fresh.

Osmosis is used in dialysis machines to filter blood of diabetic patients.

Reverse osmosis is used to get fresh water from salt water.

When you eat salt you feel thirsty because salt sucks the water out of your body cells.

When you sprinkle salt on pilled eggplants or cucumbers, water drops will form on the surface. Salt sucks the water out of the cells. Cooks do this to increase the firmness of eggplants.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
What is the effect of Salt Water on a plants growth? We all know that plants get watered by fresh water, however, would salt water do the same job? Will the plants grow better or die because of the salt water?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Independent variable (also known as manipulated variable) is the type of water. Possible values are fresh water, low salt water, and high salt water.

Dependent variable (also known as responding variable) is the plant growth. We may also observe additional independent variable such as the plant’s general health.

Controlled variables are light and temperature. We grow all test plants in the same room and under the same light and temperature conditions.

Constants are plant type, soil type, pot size.


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. This is a sample hypothesis:
Since there are no plants near salt lakes and oceans, I think the plants will probably be hurt from the salt water and will possibly die.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Introduction: In this experiment we will test the effect of salt water with different salinities on soybean plant. You may substitute soybean with other seeds such as lima bean, lentil and peas.


  1. Get four pots and 12 soaked soybean seeds.
  2. Fill each pot about 2/3 full with potting soil.
  3. In each pot , plant 3 soybean seed covering them loosely with about 1 cm. of soil (approximately the width of the seed).
  4. Label one pot with control.
  5. Label one pot with “Low salt”.
  6. Label one pot with “High salt”.
  7. Place all three pots in a tray and water with tap water until plants reach a height of 18 to 20 cm. (This will take a week to 10 days.) Make and record observations of height and any other important observation.
  8. When all plants have reached a height of 18 to 20 cm., transfer them to 3 different trays. (One tray for control, one tray for low salt and one tray for high salt).
  9. Make the “low salt” water by adding one tablespoonful salt in one liter water (If you don’t have a one liter jar, use a quart jar instead). Label the jar “Low Salt”. Mix it so all the salt dissolves.
  10. Make a “high salt” water by adding 10 tablespoonful salt in one liter water. Label the container with “High Salt”.
  11. From now on water the control pot with fresh water, water the “low salt” pot with “low salt” water, and water the “high salt” pot with “high salt” water.
  12. Continue to record your daily observations for another week.
  13. Graph the observation of height to time (days).

Materials and Equipment:

Following is a list of material used in our experiment.

  1. Soybean seeds
  2. Small pots
  3. Fresh water
  4. Low salt water
  5. High salt water
  6. Potting soil
  7. Metric rulers
  8. Trays for plants
  9. Watering cans

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Record your results in a table like this:

Plant height records from the date we used three different types of water

Date Height of control plant Height of “low salt” plant Height of “high salt” plant

Your results table will have more rows.


No calculation is required for this project.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


Write a list of your references at this section. You will need to visit a local or school library and see some books about about plants, irrigation, biology and osmosis. If you see any related material in these books, add them to your report or use them in your project.