Soils and Fertilizers
Outline of a Master Gardener Seminar
by Jennifer Moore (formerly WSU-TFREC)
What is soil?
“Soils are complex mixtures
of minerals, organic compounds, and living organisms
that interact continuously
in response to natural and imposed biological, chemical,
and physical forces.”
(From Soil Science Society of America News, June 1995)
Soils are formed as a result of 5 factors (ClORPT):
- climate
- organisms
- relief (topography
- parent material
- time
with four principal components:
- minerals
- organic matter
- water
- air
An ideal soil for plant growth will have equal amounts
of water and air
Soil Quality
The capacity of a soil to function within natural
or managed ecosystem boundaries, to sustain plant
and animal
productivity, maintain or enhance water and air
quality, and support human health and habitation (NRCS
definition).
Functions of Soil within Ecosystems
- Medium for plant growth and crop production
- Primary cleansing
and recycling medium
- Source material for construction
and medicinal products
- Sustain biological activity,
diversity, and production
- Store and cycle nutrients
and other elements
Indicators of Soil Quality
Physical properties: structure; depth of soil; infiltration
and bulk density; water-holding capacity
Chemical: pH; Electrical
conductivity; extractable N-P-K
Soil Organic Matter (SOM)
Biological: Microbial biomass;
Microbial activity
Next page: Physical Properties of Soil
Updated
July 15, 2004
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