What soil does, and what it does not do

Students will

• List the jobs soil does: it holds the plant up and stores water, air, and nutrients.
• Explain that plants do not eat soil.
• Explain that roots take in nutrients dissolved in water, so a plant can grow without soil.

New words

dissolve

To break into pieces too tiny to see and spread all through water, like sugar stirred into tea.

Talk about it

Soil does several jobs for a plant. If you took the soil away, how could you do each job another way?

Check questions and answers

1. Which job does soil do for a plant?

   • It holds the plant up (answer) Right. Roots grip the soil, the way shoes grip the ground.
   • It makes the plant's sugar Not quite. Leaves make the sugar. Think about what roots hold on to.
   • It gives the plant light Not quite. Light comes from above. Think about what roots hold on to.

2. You stir sugar into water. It seems to vanish. What happened?

   • It dissolved (answer) Right. It broke into pieces too tiny to see. It's still there.
   • It disappeared for good Not quite. Taste the water. The sugar is still in it.
   • It sank and hid at the bottom Not quite. Look closely. No pile sits at the bottom.

3. Soil gets packed down hard. There are no gaps left. What do the roots miss most?

   • Air (answer) Right. Air lives in the gaps between soil bits.
   • Light Not quite. Roots live in the dark anyway. What fills the gaps?
   • Sugar Not quite. Sugar comes from the leaves. What fills the gaps?

4. Why can a plant grow without any soil?

   • Its food can be dissolved in water (answer) Right. Roots take in food mixed into water, with or without soil.
   • Plants don't need food Not quite. Nutrients are on the list. Where else could they come from?
   • It eats air instead Not quite. Air helps, but roots still need nutrients. Think about water.