Growth without Soil
Plants need nutrients for survival. Terrestrial plants, which grow in the ground or soil, have roots to gather dissolved nutrients from the soil. But do the nutrients have to come from the soil?
In this project, you will observe hydroponic growth—that is, the growth of plants in a nutrient solution without soil. The effects of sunlight, the amount of oxygen, and the growing medium will be studied. You will also compare plants grown in soil to those grown in liquid nutrients.
Purpose: To construct a hydroponicum (hydroponic growing unit) for tomato plants.
- 5-gallon (20-liter) bucket water
- 1-gallon (4-liter) plastic milk jug with cap
- 1 tablespoon (15 ml) of plant fertilizer (5–10–5)
- 1 teaspoon (5 ml) of Epsom salt
- 1 teaspoon (5 ml) of household ammonia
- marking pen
- masking tape
- 3 dwarf tomato bedding plants
- 3 7-oz (210-ml) paper cups
- roll of paper towels
- 3 1-pint (500-ml) glass jars
- 3 1-×-1-foot (30-×-30-cm) sheets of aluminum foil
- Fill the bucket with tap water. Allow the water to stand in this open container for one day so that the chlorine in the water can evaporate.
- Prepare the nutrient solution as follows:
- Fill the milk jug one-fourth full with the dechlorinated water from the bucket
- Add the plant fertilizer, Epsom salt, and household ammonia to the water in the jug.
- Secure the cap and vigorously shake the jug to dissolve the solids.
- Add more water from the bucket to fill the jug to within 2 inches (5 cm) from the top. Rotate the jug back and forth to mix.
CAUTION: Ammonia is a poison. It and its fumes can damage skin and mucous membranes of nose, mouth, and eyes.
- With the marking pen, write "Nutrient Solution" on a piece of masking tape and tape this label to the jug.
- Remove one tomato plant from its bedding pot.
- Set the plant in the bucket of dechlorinated water and gently move it back and forth to remove as much of the soil from the roots as possible.
- Use scissors to cut a hole in the bottom of one paper cup just large enough so that the tomato plant's roots fit through. You want the root to fit snugly in the hole with about one-fourth of the root's length remaining inside the cup.
- Stuff pieces of paper towels inside the cup to give the plant support.
- Set the paper cup inside the neck of the jar to determine how far the bottom of the cup sits in the jar.
- Remove the paper cup and add enough nutrient solution so that its surface will be just beneath the bottom of the paper cup. Keep the level of the liquid the same throughout the experiment.
- Reposition the paper cup inside the jar (see Figure 16.1 on the following page)
- Surround the jar with one sheet of aluminum foil to prevent algae from growing in the liquid.
- Repeat this procedure (steps 4 through 11) for the remaining plants.
- Place the hydroponicums near a window in direct sunlight.
- Keep a daily record of the growth of the plants for as long as it takes for the plants to mature and bear fruit.
- Place the plants in larger containers as their growth requires.