g22.    What is soil?

Soil is a mixture of inorganic and organic materials. There are three soil horizons. Surface-litter layer, or O-horizon, is composed of leaves, twigs, animal waste, fungi, and so forth. Topsoil layer, or A-horizon, is made of humus and inorganic matter.  Humus and clay have negatively charged particles on their surfaces that attract potassium (K⁺), calcium (Ca²⁺) and ammonium (NH₄⁺). B-horizon is broken down rock and sand. C-horizon is basement rock. As water moves downward through the soil (infiltration) it leaches minerals and nutrients. Humification is the organic matter becoming humus. Materialization is the decomposers turning organic materials into inorganic materials.

e23.    How is soil important to plants?

m01.    How much public land is there and how is it used?

m06.    How can rangelands be responsibly managed?

m17.   What’s happening to the tropical forests?

m41.    How can matter affect the environment?

m56.    How can we increase mineral resource supplies?

m74.    How is soil important in the environment? 

m75.    How can soil be conserved? 

m76.    What contaminates soil? 

m78.    How do droughts and floods impact populations? 

m83.    How do we produce food? 

m85.    How can food production be increased?