Soil is formed through the decomposition of organic matter and rocks, weathering and erosion, and is made up of minerals, organic matter, water, and air. It exists in layers called horizons or profiles and can be sandy, clay, or loam soil depending on particle size, each with different abilities to retain air and water that plants need. Loam soil, with a mix of particle sizes, provides the best environment for plant growth by allowing both air and water in the soil.

1. Soil Properties
Foundation Science 4 Class Code SC22102

2. What is Soil made of?
Soil is made of:
1) mineral particles
2) organic matter
3) water
4) air

3. The Organic Matter in Soil
is Mostly Humus
When insects, worms, bacteria, and fungi and other
organisms die they decay and form a material called
“humus”.
As more organisms die, the soil becomes more fertile.

4. Why is Soil Important?
Much of the life on earth depends on soil
Soil is just as important as water, air, and sunlight.
– Without soil, there would be no plants.
– Without plants, there would be no food, shelter or
oxygen to breathe for humans or animals.
Soil provides the
nutrients needed by
most plants to grow.

5. How are Soils Formed?
1. Decomposition –
animals and plants
die and “feed” the
soil

6. How are Soils Formed?
1. Decomposition
2. Weathering (not
moving)– rain and
wind break rocks
down into soil

7. How are Soils Formed?
1. Decomposition
2. Weathering
3. Erosion (moving)–
when the rocks
break and fall apart
in the wind or rain

8. Soil Profiles
• Soil forms in layers.
• The set of layers is
called a profile.

9. Soil Profiles
• Sometimes the
layers are called
horizons.

10. Types of Soil
Three Types:
1) Sandy soil contains large particles. Sandy
soils stay loose and allow moisture to
penetrate easily, but do not retain it for long
term use.
2) Loam soil is a mix of sand, silt or clay, and
organic matter. Loam soils are loose and look
rich.
3) Clay soils are made of very small particles.
They feel slick and sticky when wet.

11. Clay Soil is Slippery and Holds Water Up
Remember, the
particles in clay
soil are very small

12. Sandy Soil does NOT Hold Water
Sandy soil has
large particles and
holds air but not
water

13. Loam Soil holds both Air AND Water
Loam soil has
both large and
small particles an
holds water and
air well

14. All Three Soils…
Loam Soil Clay Soil
Sandy Soil

15. What do Plants Need to Grow?
1. Air
2. Water
3. Nutrients Soil responsible for these 3
4. Sunlight
So, if soil does not have a lot of air, plants won’t grow well.
This is why clay soils are bad for plant growth.
If soil does not have a lot of water, plants won’t grow well.
This is why sandy soils are bad for plant growth.
Loam soils can hold water and air, and are the best for
plant growth.

16. Types of Soil Video

17. Questions
1. What is soil made of?
2. What is humus?
3. What are 2 reasons why soil is important?
4. How are soils formed?
5. What is a soil profile ?
6. What are the 3 types of soil?
7. Which soil is best for plant growth?
8. What are the 4 things a plant needs to grow?
9. A plant needs 4 things to grow, how many does it get from soil?
10. Why are clay soils bad for plants to grow?
11. What is sandy soil good at holding?
12. What soil type is probably under this water?