1059 Main Avenue, Clifton, NJ 07011

The most valuable resources for teachers and students

(973) 777 - 3113


1059 Main Avenue

Clifton, NJ 07011

07:30 - 19:00

Monday to Friday

123 456 789


Goldsmith Hall

New York, NY 90210

07:30 - 19:00

Monday to Friday

How does the amount of water affect plant growth?

How does the amount of water affect plant growth?

Introduction: (Initial Observation)

Plants are living things. They live in places all around the world. Plants can grow in deserts, rain forests, and even in your own backyard. But no matter where plants grow they all need soil, water, air, and sunshine. A plant’s needs change as it grows. Plants need a lot of water during early growth, flowering and fruit set.

In this project we will try to see how does the amount of water affect the 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 nutrients for plants. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from.

This is a sample of the information you may find:

Indoor Plants – Watering

The main cause of death of potted plants is over-watering. Roots need both water and oxygen, and when surrounded by water, they cannot take up oxygen. These roots may rot and eventually the whole plant may die. The symptoms of over-watering and underwatering are similar. Both lead to poor root health, root decline and possibly death of the plant.

A common question from gardeners is “How often should I water my plants?” There is no pat answer to this question. The amount and frequency of watering depends on many factors, such as the plant species, its growth stage, its location, the type and size of its pot, soil mix characteristics and variable weather conditions.

There is a wide range of watering requirements for different species of plants. Plants with large or very thin leaves and those with fine surface roots usually require more frequent watering than succulent plants with fleshy leaves and stems that are able to store water. Some plants thrive under moist conditions while other plants grow well when kept drier.

Plants may slow in growth after a flush of new growth or a heavy flowering. During these periods and while it is dormant, a plant will need less water.

Water evaporates rapidly from the sides of a porous clay pot, which requires more frequent watering than nonporous, glazed or plastic pots. A large plant in a small pot needs water more often than a small plant in a large pot.

Different soil mixes require different watering schedules. Heavy, fine-textured potting media and those that contain a lot of peat moss hold more moisture than loose, porous mixtures of bark, sand and perlite.

A plant in a warm, dry, sunny location needs more frequent watering than one in a cool, low-light environment.

The rule-of-thumb is to water when necessary. The following methods may be used to determine when to water:

    • Touch the soil – The most accurate gauge is to water when the potting mixture feels dry to the touch. Stick your finger into the mix up to the first joint; if it is dry at your fingertip it needs water.
    • Tap the pot – When the potting mix in a clay pot begins to dry, it shrinks away from the sides of the pot. Rap the side of the pot with the knuckles or a stick. If the sound is dull, the soil is moist; if the sound is hollow, water is needed.
    • Estimate weight – As potting mixtures become dry, a definite loss in weight can be observed.
    • Judge soil color – Potting mixtures will change from a dark to lighter color as they dry.

There are a number of watering meters available to measure moisture in the soil, indicating whether water is needed. These products vary widely in accuracy. The readings can be influenced by factors other than soil moisture content. Fertilizer and soil type can affect the reading.

When watering is required, water thoroughly. Apply water until it runs out of the bottom of the pot. This washes out the excess salts, and it guarantees that the bottom two-thirds of the pot, which contains most of the roots, receives sufficient water. Don’t let the pot sit in the water that runs out. Empty the saucer.

Do not allow the soil to become excessively dry. If the salt level in the container is high, root damage may occur. If soil does become very dry and hard to rewet, use the double watering method. Water once and then again half an hour later; or place the pot in a sink or a bucket of water. Remove the pot when the soil surface is moist. Allow the pot to drain completely. If peat is allowed to dry completely, not only is it difficult to rewet, it also will not hold as much water as it could hold before it dried.

Do not water with hot or cold water. The water temperature should be between 62 and 72 °F.

Do not water plants with softened water because sodium and chloride will also be added to the soil mix, possibly causing plant damage.

Although wilting is often an indication of the need to water, it is not always so. Any injury to the root system decreases a plant’s ability to take up water, including root rot, which is caused by too much water. This inability to take up water will cause wilting, and under these conditions, watering may make the problem worse.

Why Do We Fertilize Plants?

For centuries plants grew without any help from human beings, and many are doing so today. Thus, it is obvious that they can do so by themselves, especially in environments to which they are adapted. However, as humans cultivated plants it was learned that the addition of certain materials to the soil sometimes caused plants to respond with characteristics which were considered to be desirable (e.g., more fruit, faster growth, better color, more attractive flowers). Early in recorded history we find accounts of applications of animal manures, wood ashes, and lime to enhance plant performance. Thus was born the practice of fertilization and soil amendment.

We should note here that the plant responses we get from applying fertilizer and other soil amendments are not inherently “good” or “bad.” These terms are subjective and reflect personal judgment as to what is “desirable.” For example, a greater quantity of fruit which is too small for market is not a characteristic desired by a peach farmer. Faster growth is usually not a desirable effect for someone growing bonsai plants. Rank vegetative growth is not desirable in an already-lush lawn nor are profusely-blooming squash plants that are not setting fruit. Thus, a “good” response to fertilization under one set of circumstances may be a “bad” response under another set. It depends on what response the person wants from the plant.

So, why do we apply fertilizer to the soil? Because we want to obtain some desired plant response. We want our plants to “do better.” As we set out to fertilize our plants we should keep in mind how we want them to do better (grow faster, produce better flowers or fruit, etc.) – and we should also know if fertilization will contribute to that improvement.

When Should I Apply Fertilizer?

Stated simply, you need to fertilize whenever you expect to get a desired plant response. However, the difficulty is in predicting. You usually want to know in advance if there will be a response to added fertilizer so that you can avoid growing plants under nutrient-deficient conditions. Since predicting plant responses is difficult, many people apply fertilizer as insurance against nutrient deficiencies. The result: over fertilization in the United States is now as prevalent a problem as under fertilization.

A suggested approach to fertilization involves the following steps:

    • Recognize what plant response you are seeking;
    • Determine from observation or consultation if fertilizer application is likely to give you the response you want;
    • Apply fertilizer only if your desired response is likely;
    • Apply only the amount of fertilizer necessary to give the desired response.

What Nutrients Do My Plants Need?

The best way of knowing what your plants need is by observing plant performance and understanding the multiple factors affecting such performance (e.g., light, water, temperature, pests, nutrition).

There is no magical way of knowing which nutrient may be in limited supply in the soil. Soil testing helps predict the need for some of the nutrients, but testing is only one of the tools in plant nutrient management. If you recycle organic matter such as grass clippings (don’t use a bag on your mower) and leaves, you will be returning to the soil the nutrients those plants had absorbed. It is the easiest, least expensive, and most environmentally sound way to fertilize. You may still have to supplement, but you will then apply fewer nutrients–and a lot less fertilizer. Plants need 18 elements for proper growth and reproduction. Under many conditions, plants obtain enough of these elements from the soil, water, and air. It is only in certain environments and growing conditions that one or more of the nutrients are deficient.

The most-commonly applied nutrients are nitrogen (N), phosphorus (P), and potassium (K). Responses to all three elements were fairly widespread in the past, and it became customary to apply the three together. As a result of habit, all three are still applied even though there are now many situations, especially in gardens and landscapes, where plants do not respond to one or more of these fertilizer nutrients.

Other plant-essential nutrients used in fairly large quantities are calcium (Ca), magnesium (Mg), and sulfur (S). However, fertilization with these nutrients is not usually necessary because the Ca and Mg contents of soil are generally sufficient for most plant species. Also, large quantities of Ca and Mg are supplied when acidic soil is limed with dolomite. Sulfur is usually present in sufficient quantities from the slow decomposition of soil organic matter, an important reason for not throwing out grass clippings and leaves.

Micronutrients are those elements essential for plant growth which are needed in only very small (micro) quantities . These elements are sometimes called minor elements or trace elements, but use of the term micronutrient is encouraged by the American Society of Agronomy and the Soil Science Society of America. The micronutrients are iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), boron (B), molybdenum (Mo), Cobalt (Co), Nickel (Ni), and chlorine (Cl). If one of your plant species has a micronutrient deficiency, apply the recommended rate of the deficient nutrient. Recycling organic matter such as grass clippings and tree leaves is an excellent means of providing micronutrients (as well as macronutrients) to growing plants.

What About Organic Matter as a Source of Nutrients?

Organic matter (such as grass clippings, tree leaves, shrubbery and tree trimmings) is an excellent source of plant nutrients. The plants which produced that organic material accumulated all the essential nutrients for their own growth needs. Upon decomposition, those nutrients in the organic material become available for reuse. When you recycle “homegrown” organic matter such as grass clippings, leaves, and shrubbery trimmings you are practicing an excellent method of fertilizing your landscape. You are keeping valuable materials on site and are also greatly reducing the municipal solid wastes placed at curb side. Other organic materials, such as animal manures, biosolids (processed sewage sludge), or various composted materials, are also alternative sources of plant nutrients.

Question/ Purpose:

The purpose of this project is to determine how does the amount of water affect the plant growth (i.e. plant height, stem volume).

Identify Variables:

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.

Independent variable (also known as the manipulated variable is the amount of water used to grow the plant.

Dependent variable (also known as responding variable) is the plant growth (plant height).

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


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.

My hypothesis is that more water will result more growth.

Experiment Design:

In order to test how does the amount of water affect the plant growth, we plant some seeds and use them to test the effect of water.

Experiment 1:

Materials: radish seeds (one packages will be enough for multiple experiments), water, paper towels, plastic beverage cups, aluminum foil, liquid fertilizer (plant food purchased from the grocery or home supply store)


  • Soak the radish seeds in water for about an hour.
  • Fold a paper towel lengthwise and float it in a shallow pan of water. Remove it and gently wring out the excess water.
  • Get 6 soaked radish seeds
  • Lay the soaked seeds along the folded edge of the moist paper towel. Roll the paper with the seeds into a cylinder, as in the diagram.
  • Repeat with the above steps ten times until you have ten rolled paper towel with 6 seeds in each of them.
  • Place the rolled paper cylinders in separate plastic beverage cups
  • Label one of the cups as a control and label the others with numbers from 1 to 9 . One represents the least amount of water and 9 represents the highest amount of water.
  • Add the necessary nutrients to one gallon of water that will be used for our experiment.
  • Each day add 10 drops of water to cup number 1, 20 drops of water to cup number 2, 30 drops of water to cup number 3 and continue with the same increment so the cup number 9 will get 90 drops of water each day.
  • Place a piece of aluminum foil loosely over all four cups and allow the cups to remain undisturbed until the seeds germinate (2 to 4 days)
  • Once the seeds have germinated, remove the foil and place the cups in a location that provides them with light.
  • Measure the roots and the shoots of the growing plants and chart the growth of their seedlings every day or two.
  • Describe the effect of water amount on the growth of the seedlings.

Above description is for testing 9 different amounts of water. If you want to test more or less samples, you can modify the experiment as needed.

The reason that we place 6 seeds in each paper towel is to see the average result, not the result of an accidentally large seed.


Experiment 2:


1) Plant 6 bean seeds in 6 small pots filled with potting soil. Place the seeds at the same level in soil for all pots. Place the pots by a sunny window.

2) Label each pot with numbers from 1 to 6

3) Water the pots every day. Each time the pot number 1 will get the least amount of water and the pot number 6 will get the most.

4) Make daily observations and record the height of you plant every day for two to three weeks.

If you need a control, get an additional small pot in which you plant a bean seed, but you don’t water it at all.

Experiment 3:

How does excess amount of water affect plants?

3 plants*, 3 dishes or pans, water, crayons, graph paper

* make sure you choose plants that are the same kind of plant, as close to the same size as possible and healthy


1. Label the plants A, B, and C. Make holes in the bottom of the containers of plants A and B. If your containers already have holes, plug up the holes in the bottom of container C.

2. Place each plant in a dish and put all three plants in the same location where they will receive the same light.

3. Water plant A every other day, keeping the soil moist but not wet. Do not water plant B. Water plant C every day, keeping the soil saturated, very wet.

4. Make a bar graph showing the color of each plants leaves every day for a week.

Think About This:

1. What happened to the color of plant A? plant B? plant C?

2. Does it matter how much water a plant gets?

3. Is drainage important?

Materials and Equipment:

  • Radish seeds (one packages will be enough for multiple experiments)
  • Water
  • Paper towels
  • Plastic beverage cups
  • Aluminum foil
  • Samples of liquid fertilizers (plant food purchased from the grocery or home supply store)
  • Pots for experiment 2
  • Bean seeds for experiment 2

Results of Experiment (Observation):

Record the results of your experiment 1 in tables like this:

This table shows the average height of seedlings in each cup in different days starting day 4.

control cup 1 cup 2 cup 3 cup 4 cup 5 cup 6 cup 7 cup 8 cup 9
day 4
day 5
day 6
day 7
day 8

Questions :

1) Why did you need 10 cups to perform this experiment? What conclusion could you draw if you had performed the experiment with only one cup?

2) What effect did the amount of water have on the plant growth?

If you are performing experiment 2, make a similar table for the results of experiment 2.

Pot 1 Pot 2 Pot 3 Pot 4 Pot 5 Pot 6
day 4
day 5
day 6
day 7
day 8


You may need to calculate the average heights of seedlings in each paper towel.

Summery 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.


Find and review some books about plants, nutrients and fertilizers.