Module 5. Soil

(Level of difficulty **)

Question: How does type of soil affect seed germination and plant growth?

Materials you will need:
•Several empty rinsed plastic yogurt containers or single-use cups (as many as the number of different kinds of soil you wish to compare; any size, preferably 3-10 oz)
•Larger plastic or Styrofoam tray(s) or bowl(s)
•An awl
•Different kinds of soil (for example, sand, red clay, dirt from school yard, backyard, park, etc.)
•Seeds (bean, pea, cucumber, tomato, sunflower, corn, pumpkin or squash)
•Water (tap water is fine)

•Poke small holes (1-3 per container) on the bottom of yogurt containers or cups using an awl (have an adult help you with that!)
•Fill containers with different types of soil and place them in a larger bowl/tray (to capture spills and leaks)
•Pour some water onto the soil to make it moist, but do not overwater (stop watering as soon as you see excess water coming out from the holes onto the tray)
•Put the seeds in soil (it is OK to put multiple seeds into each container, but keep the number of seeds in all containers the same) and cover them with a little bit of soil (finger-thick layer or less); remember to use the same kind of soil to cover the seeds, as you used to fill the pot
•Put both containers next to the source of light (a windowsill).
•Wait for 3-14 days for the seeds to germinate
•Observe plant growth over time

Helpful hints and suggestions:
•Don’t forget to label the containers (for example “park” , “schoolyard”, “playground”, and so on), so after your experiment is done you will not get confused which pot is which.
•Dependent on what kind of seeds you planted and how fresh they are, it may take a very different amount of time for the seeds to germinate and grow.
•Don’t forget to water your plants! The easiest way to water the plants is to add water to the dish/tray your pots are sitting in: the soil and the plant roots will take up the water through the hole that you drilled!

Expected results:
•Seeds in different types of soil may germinate at different times: some types of soil are better than others for germination.
•Once seeds germinate, plants would grow differently in different types of soil.
•Different kinds of soil keep different moisture levels.

Follow-up questions:
•Why do you think plants prefer one type of soil over the other?
•Which soil characteristics [such as density (compactness), color, particle size, nutrient content, moisture level and so on] do you think are the most important for plant growth?
•Do different plant species prefer the same or different kinds of soil?
•If you were to repeat the experiment, would you get the same results?
•What would happen if you used another kind of seeds or did the experiment in the dark?