1. Food, Soil, and Pest Management
Chapter 12

2. Science Focus: Soil is the Base of Life on Land
Soil is a complex mixture of:
Eroded rock
Mineral nutrients
Decaying organic material
Water
Air
Billions of living organisms – most of them are microscopic decomposers

3. Science Focus: Soil is the Base of Life on Land
Soil is a renewable resource, but it is renewed very slowly.
Depending on the climate, the formation of 1 cm of soil could take from 15 to 100 yrs.

4. Science Focus: Soil is the Base of Life on Land
Soil is the base of all life on land.
The nutrients that are passed on from producers to consumers come from the soil.
Human agricultural activities greatly accelerate natural soil erosion…and could make it a nonrenewable resource.

5. Layers in Mature Soils
Mature soils are arranged in a series of horizontal layers called soil horizons.
O Horizon – (surface litter layer) leaves, twigs, and other organic materials
A Horizon – (topsoil) composed of mostly of humus – partially decomposed organic matter
B Horizon – (subsoil) mostly inorganic material like rock pieces, sand, and clay with small amounts of organic matter from the A Horizon
C Horizon – (bedrock) the un-weathered parent material

6. Science Focus: Soil is the Base of Life on Land

7. Layers in Mature Soils

8. Layers in Mature Soils
Infiltration: the downward movement of water through soil.
Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers.
The soil type determines the degree of infiltration and leaching.

9. Soil Profiles of the Principal Terrestrial Soil Types
Most cropland is on soil that was exposed by the clearing of grasslands or deciduous forests.
Some biomes have very poor soil.

10. Soil Types
There are as many as 15,000 different types of soil in the U.S. alone.

11. Soil Properties
The large variety of soils is a result of the large variety of the different combinations of soil properties:
Soil Texture
Particle size
Moisture content
Organic matter
Bulk Density
Fertility – N,P,K, pH
Porosity / Permeability