FERTILIZERS

Something's Fishy About That Fertilizer

 http://www.sciencebuddies.org/science-fair-projects/project_ideas/EnvSci_p017.shtml

Abstract

Did you know that when you use fertilizer in your garden, it can eventually reach a lake, stream, or pond? There are many different chemicals present in fertilizers. How will they affect the aquatic organisms in the ecosystem? In this science project you will get to find out!

Objective

Test the effects of liquid fertilizer on an aquatic environment containing small aquatic animals and plants.

Introduction

Fertilizers are chemicals that are added to the soil to increase the growth of plants in yards, gardens, or large agricultural facilities. The effect on crops can be increased growth, but fertilizers can have a negative impact on surrounding organisms in the soil.
When a heavily fertilized field is irrigated, excess water can flow along the surface of the land and pick up the fertilizers. This is known as surface runoff. The fertilizer-rich surface runoff can directly flow into nearby streams, lakes, or ponds, like the one shown in Figure 1, below. Additionally, chemicals present in the fertilizer can also infiltrate the ground water system and contaminate it. This polluted ground water can also make its way into nearby ponds, streams, or lakes. What happens to the aquatic organisms that are present in the environment when chemical fertilizers are present? How do the fertilizers affect the organisms' ecosystem?

Figure 1. How are the organisms in aquatic environments, like this pond shown here, affected by the chemicals from fertilizers?

In this science project you will test the effect of liquid fertilizer on an aquatic environment. Each aquatic environment will be a mixture of small aquatic plants and animals. By adding different brands of fertilizer, you can test how they affect the environment. Which fertilizers are the best choice for the environment?

Terms and Concepts

• Fertilizers
• Surface runoff
• Ground water
• Contamination
• Ground water pollution
• Ecosystem

Questions

• How will fertilizer affect an aquatic environment?
• Will all of the organisms be affected similarly or differently?
• Which brand(s) of fertilizer will cause an effect?
• Are organic fertilizers less toxic to aquatic ecosystems? 

Materials and Equipment 

100 mL graduated cylinder. Alternatively, a metric measuring cup may be used.

• pH test strips
• Small aquatic animals, such as small pond snails. 
• Small aquatic plants, such as duckweed or Elodea (at least 40 if you are using smaller plants, like duckweed, or at least 12 if you are using larger plants, like Elodea). Pick one or two different types. Alternatively, these may be available from aquarium supply stores, ponds, or plant nurseries.

You will also need to gather these items:

• Large, sealable, reusable plastic containers with lids, e.g., Glad or Zip-lock (4). These should each hold at least 1400 mL, or about 6 cups.
• Permanent marker for labeling
• Distilled water (2 gal.). This is available in most grocery stores.
• Different brands of liquid fertilizer (3). You can find these at plant nurseries, the plant section of a hardware store. These may also be called "plant food," but you will want to confirm with a sales person at the store that these are also considered fertilizers.
• Lab notebook

Experimental Procedure

1. Rinse each container thoroughly with water. Do not use soap because it can coat the plastic container and may be harmful to the organisms in your experiment.
2. Assign a number (from 1 to 3) to each fertilizer you use. Use a permanent marker to label the fertilizers' bottles, or just write the numbers you assigned in your lab notebook.
3. Label each container "1," "2," or "3" with a permanent marker. Also label one container "Control."
4. In your lab notebook, make a data table like Table 1, to record your data in.
5. Use a graduated cylinder or metric measuring cup to prepare the solutions for each container according to Table 1. Prepare one container for each fertilizer, making sure the numbers on the containers match the ones you assigned to the fertilizers. In the container you labeled "Control," only fill it with distilled water, but no fertilizer, since it is your positive control. Use bottled distilled water, not tap water, because tap water may contain chemicals, like chlorine or chloramine, harmful to aquatic life.

Fertilizer Number	Amount of Water (mL)	Amount of Fertilizer (mL)	Total Volume (mL)	pH	Observations
1	975 mL	25 mL	1000 mL
2	975 mL	25 mL	1000 mL
3	975 mL	25 mL	1000 mL
Control (distilled water only)	1000 mL	0 mL	1000 mL

Table 1. Prepare your containers based on this data table. You will want to prepare one container for each experimental fertilizer group, and one container that only has distilled water in it (and no fertilizer) for your control. The amounts of water and fertilizer needed are given in milliliters (mL).

6. Check the pH of each container with your pH test strips and record the data in your data table. Also record any observations about the fertilizer or container you put it in.
7. Evenly distribute the aquatic animals into each container, putting at least 5 into each container. If you are using more than one type of animal, make sure there is the same number of each animal type in each container.
   1. If you are using Daphnia, you can use a watering pipet or medicine dropper to move them from one container to another.
8. Put 3 to 10 plants into each container, depending on the size of the plant.
   1. For example, if you are using small duckweed plants, 10 is a good amount, while if you are using the larger Elodea plants, 3 plants in each container is a better amount.
   2. If you are using duckweed, make sure that each plant has a stem (the part sticking down).
   3. If you are using large Elodea plants, you can carefully cut them into smaller pieces, about one or two inches long, so it is easier to count their leaves.
9. In your lab notebook, make data tables like Table 2 and Table 3. In Table 2, write down the total number of animals in each container. In Table 3, write down the total number of plant leaves in each container.
   1. Note: If you are using more than one type of animal or plant, you can make another data table like Table 2 or Table 3 and separately record each type of animal or plant in its own data table.
10. Each day, for five days, write down your observations in your data tables. Specifically, count and write down the total number of animals that are alive in each container, and the total number of plant leaves in each container.

Fertilizer Number	Number of Animals Living
	Day 1	Day 2	Day 3	Day 4	Day 5
1
2
3
Control (distilled water only)

Table 2. Each day, write down the total number of animals alive in each container. Note: If you are using more than one type of animal, you can make a second data table like this one and record each type of animal in their own data table. Put the name of the animal type in the title of the data table.

Fertilizer Number	Number of Leaves on Plants
	Day 1	Day 2	Day 3	Day 4	Day 5
1
2
3
Control (distilled water only)

Table 3. Each day, write down the total number of leaves in each container. Note: If you are using more than one type of plant, you can make a second data table like this one and record each type of plant in their own data table. Be sure to correctly title the data tables.

11. Graph your results.
    1. You can make line graphs by hand or on a computer using a program like Create a Graph and then print the graphs out.
    2. Make one line graph that shows the number of animals living in each container over time. On the horizontal axis (x-axis) put the time (in days). On the vertical axis (y-axis) put the number of animals living. Make a line for each container you tested, including the control.
       1. Note: If you tested more than one type of animal, you can make a separate graph for each animal type.
    3. Make one line graph that shows the number of plant leaves in each container over time. On the x-axis put the time and on the y-axis put the number of plant leaves. Make a line for each container you tested, including the control.
       1. Note: If you tested more than one type of plant, you can make a separate graph for each plant type.
12. Analyze your results and see if you can draw conclusions about how the different fertilizers affected the animals and plants.
    1. Did one type of fertilizer affect the animals more than another type of fertilizer? What about the plants?
    2. Did the animals and plants respond similarly or differently to the fertilizers?
    3. Overall, which seemed to be the least toxic? Which seemed to be the most toxic?