Soil in the Farm Ecosystem

Soil is where life on the farm begins. Soil provides some of the nutrients that a farmer's crops need to grow. Plants make most of the food they need to grow from the water in the soil and the air.

Straw graphic Why do you think some farmers consider soil the most important thing on their farm?

Soil is made up of different sizes of particles and different layers. Farmers need to know what kinds of particles are in their soil and how thick the layers are in their fields in order to decide how much and how deep to plow or irrigate.

Eco Info
There are 20,000 different types of soil in the United States!

Straw graphic What particles are in the soil near you?

"The bacteria that digest organic material basically live in the top four to five inches, what we call the digestive system of the soil."
Rex Spray, Morgan Township

Eco Info
A half teaspoon of soil contains millions of bacteria and other microorganisms!

Soil Profile
Organic Material Dead plants and manure are plowed under by the farmer to be converted by earthworms and bacteria into humus.
Topsoil Humus is created by worms and bacteria and contains the important nutrients: nitrogen, phosphorous and potassium.

Subsoil Minerals and soil particles are carried down from the topsoil by water.

Bedrock Broken down rocks store water to be absorbed by long plant roots.

Image from Cunningham and Saigo, Environmental Science: A Global Concept, 1997

Eco Info
Only one millimeter of topsoil is created on 2.5 acres every year!

In addition to having the enough nitrogen, phosphorous, potassium and water for plants to grow, soil needs to have the correct balance of acidity, which is measured by testing the pH. Farmers may add nutrients to the soil or change the pH of the soil by adding chemicals. Other problems farmers may have with their soil are erosion and compaction. Soil compaction occurs when heavy tractors and combines make the soil hard by compressing the air and water spaces in the soil.

Straw graphic Conduct an experiment to find out how some farmers prevent erosion.
Straw graphic What ideas can you think of to reduce the compaction of farm soil?

Compacted soil photo

The left hand holds compacted soil while the right hand holds humus.
Photo from Nebel and Wright, Environmental Science: The Way the World Works, 1996
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