You’ve seen how animals on a farm need healthy soil. Plants grown for food need healthy soil, too.
Remember how soil is made partly of tiny bits of rock? These bits have come from bigger rocks that have been broken down by ice, wind, and water.
Rocks are made of minerals. When they’re broken down through time, they add the minerals to the soil. These minerals are nutrients that are important to help living things grow and thrive.
ESSENTIAL QUESTION
How does weather cause the earth to change? How does this change the soil?
Plants start with seeds. Have you ever planted a garden? If so, you know that the seeds for different plants look different. Some seeds are large and flat, others are tiny and round. Some you can actually eat, such as sunflower seeds. No matter how different they look, all seeds work the same way.
To plant, you bury a seed in the soil. When it rains, moisture seeps through the soil and softens the skin of the seed. The seed swells a little bit and splits open. Then the seed begins to grow. The root pushes down into the soil while the shoot pushes up in the other direction, toward the surface.
Once that shoot breaks through the surface of the soil, it runs out of its own energy. That’s when the sun takes over. It shines on the seedling and gives it the energy it needs to keep growing into a full-sized plant.
WORDS to KNOW
Ice Age: a period of time when ice covered a large part of the earth.
You’ve seen how the soil is full of living organisms, all working together to keep the soil healthy. These organisms help plants, too. Underground creatures, such as earthworms, create tiny tunnels in the soil. They push the soil around near the roots of the plant, and help the air and water work their way through the soil to the plant.
PLANT POWER!
When you look at seedlings, they look pretty fragile. But they’re actually fairly tough. As long as there is soil, sunlight, air, and water, they go to work getting stronger every day.
Plants are helping the soil, too. When the soil is wet, plants draw water out of the soil through their roots. Some roots help break up rocks over time, which makes even more soil. Plants and their root systems also help hold soil in one spot. When nothing anchors soil down, wind or water blows it away or washes it away in a process called erosion.
WORDS to KNOW
erosion: the gradual wearing away of rock or soil by water and wind.
Back in the 1930s, people in the United States discovered how important plants are to prevent erosion. Farmers on the prairies overworked the land. They plowed up the soil and planted crops that needed a lot of rain.
Unfortunately, there were several years with very little rain. The topsoil got so dry and unhealthy that strong winds just blew the soil away. The prairie area became known as the Dust Bowl because the wind created such terrible dust storms.
Since then farmers have figured out how to work their land in ways that help prevent it from drying out. This keeps the soil healthy and rich.
It’s hard to imagine the size of the dust storms that destroyed the prairies, but you can see actual videos of them.
KEYWORD PROMPTS
1930s great dust storm 
Plants depend on many different nutrients to grow. Some of these, such as hydrogen, carbon, and oxygen, come from the air and water. These help plants in a process called Photosynthesis. This is when a plant changes sunlight, water, and carbon dioxide into the energy it needs to grow.
WORDS to KNOW
photosynthesis: the process in which plants use sunlight, water, and carbon dioxide to create energy.
Plants get mineral nutrients from the soil. These include nitrogen, potassium, calcium, and iron. Do you take a multi-vitamin every day? If you look at the bottle, you’ll see some of these same nutrients you need to grow, too! Since plants can’t get them from taking vitamins, they depend on the soil to provide them.
If the soil is healthy, then the plants will grow strong. To be healthy, though, farmers can’t plant the same crops in the same place year after year. There need to be plenty of helpful organisms and nutrients in the soil. Nutrients can be added to the soil to enrich it and help plants grow.
ESSENTIAL QUESTION
Now it’s time to consider and discuss the Essential Question: How does weather cause the earth to change? How does this change the soil?
FLOWER POWER
With this experiment, you can see how water and nutrients are pulled up through the roots of a plant. Start a scientific method worksheet.
SUPPLIES
1 empty water bottle for each flower
water
food coloring
freshly cut white carnations
scissors
science journal and pencil
1 Remove the labels from the water bottles so you can see inside the bottles easily. Fill each bottle about one-third full of water.
2 Add about 15 drops of color to the water, one color per bottle.
3 Cut the end of each carnation’s stem at an angle. Place one in each bottle.
4 Put your flowers in a sunny spot and come back a few hours later to check on them. Don’t worry if you don’t see a change! Keep checking at least twice a day for several days. Record your observations in your science journal.
WHAT’S HAPPENING? Since the flowers are cut, they no longer have roots to pull nutrients and water from the surrounding soil. But they continue to draw water up through their stems, bringing the food coloring along with it. When the water evaporates from the petals and leaves of the flowers, the dye is left behind, coloring your flowers.
DRINK UP!
Sometimes weather conditions aren’t perfect for plants. How much water do plants really need to thrive? By controlling how much water several different plants get, this experiment will help you find out.
SUPPLIES
several containers for plants, such as paper cups or small pots
potting soil
bean or sunflower seeds
science journal and pencil
ruler
water
measuring cup
1 Put the same amount of potting soil and plant seeds at the same depth in each container. Try to keep all conditions the same for each pot, including a sunny spot to watch them grow.
2 Start a scientific method worksheet. Make a chart with a row for each plant. Across the top, put the dates on which you measure each plant’s growth.
3 Give each plant the same amount of water, but change how often you water each plant. For example, water Plant A twice a day. Water Plant B every day, Plant C every other day, and Plant D every third day.
4 When seedlings start to poke up from each container, start measuring them and marking it on your chart. What do you find? Does one plant do better than the others? What is the difference in the way the plants look? Is one greener or taller? What does that tell you about plants and water?
ROOT WINDOW
Have you ever wondered what it looks like when the roots start pushing down from a sprouting seed? With this project, you’ll be able to sneak a peek!
SUPPLIES
paper towel
clear plastic zip bag
radish or sunflower seeds
water dropper
tape
science journal and pencil
1 Carefully wet the paper towel, squeeze out the excess water, and flatten it into a square that fits in the plastic bag. You want the paper towel wet, but not dripping.
2 Put the wet paper towel into your plastic bag, keeping it flat. Carefully place several seeds on the middle between the plastic and paper towel. Using the water dropper, add a couple more drops of water to the paper towel near the seeds. You don’t need to close the bag.
3 Tape the bag to a sunny window so the seeds face the glass.
4 In two days, check on your seeds. If the paper towel is drying out, add some drops of water. What do you see? Check on your seeds every day. What’s happening? Record your observations in your science journal. Make sure the paper towel stays damp.
5 When the roots are long, you can take the seeds out and transplant them into soil.
THINK ABOUT IT: Why can seeds sprout without soil? How long can a plant grow without soil?
PENNY POWER
It’s hard to believe a tiny seedling is very strong. But if it’s grown in healthy soil with proper sunlight and water, it can be pretty powerful! After all, it’s got to push through the soil and break through the surface. Here’s a fun project to see just how strong those plants can be.
SUPPLIES
small container
potting soil
bean seeds
toothpicks
penny
science journal and pencil
1 Fill the container with soil. Gently press a small hole into the soil about 1 inch deep in the middle of the container. Drop in a seed. Cover with soil and lightly water until the soil is damp but not soaking wet. Place your container in a sunny spot.
2 When the seedling pokes through the soil, press four toothpicks into the soil to form a square around the place you planted the seed. Push them into the soil about halfway.
3 Gently place a penny inside your toothpick square, using the toothpicks as guides to hold the penny in place. Your penny will be resting on top of your plant.
4 Continue caring for your plant. What happens? How strong is your plant? Record your observations in your science journal.
