The nature of resources Chapter 8 pp135140 Soil Characteristics There are several characteristics of soil that affect its value for farming and growing vegetation Organic Content Soil ID: 329913
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Slide1
World Geography 3202Slide2
The nature of resources
Chapter 8 (pp.135-140)Slide3
Soil Characteristics
There are several characteristics of soil that affect its value for farming and growing vegetation.
Organic
Content
Soil
fertility is determined as a ratio of the organic content (residues of plants and animals
) versus the content of ground bed rock. Mineral content varies with precipitation because heavy rains tend to leech soils removing minerals from the root region of soil (calcium, magnesium, potassium, nitrogen). Slide4
Soil
Texture
refers
to the mixture of fine particles (sand), very fine particles (silt) and extra fine particles (clay). The best texture for agriculture is an even mixture of each. Slide5
Soil Profile
There
are fairly distinct layers within soil.
Top Layer: Dark color &
rich
in humus. The thickness and quality of the top humus layer is very important for plant life.
2nd Layer: Mineral layer deposited from above (calcium, magnesium, potassium, nitrogen)3rd Layer: Weathered bed rock 4th Layer: Bed rock Slide6
A Soil ProfileSlide7
Types of Soil
Podzol
soils which predominate the boreal forest and tend to be somewhat acidic
Chernozem
soils which tend to be the best for agriculture. They are found in grasslands which are semi-arid resulting in less leeching and a mineral rich soil. Slide8
Latosol
soils
which are very infertile due to the high amount of leeching. They are found in tropical rain forests with high amounts of rain which result in leeched mineral-poor soil. Slide9
Environmental Factors & Soil
Temperature
affects
the development of humus. Too cold and the decay of organic matter is slowed considerably.
Precipitation
affects
the mineral content of soil.too much rain and minerals are “leeched” down beyond the reach of plant roots. The process of leeching is also called “eluviation”Slide10
Soil Texture
Soil texture refers to the size of particles in the soil.
stones are approximately baseball-sized;
gravel
is small stones;
sand is fine particles;
silt is very fine particles; clay is extremely fine particles. Slide11
Soil is predominantly composed of sand, silt and clay
. Its
texture is determined by the mixture of these three
.
The
best agricultural soils are an even mixture of all
three!The best mixture of all three (sand, silt and clay) is called Loam.Slide12Slide13Slide14
Consider…
What makes the best soil?
40% sand, 20% clay and 60% silt
OR
30% sand, 60% clay, or 10% silt
The answer is A! Remember loamy soil is the best!!Slide15
Threats to Soil
Poor soil
management: can
lead to loss of fertile
soil.
While
the earth's surface is covered in soil the amount of fertile soil valuable for agriculture is limited and is dwindling yearly.Expanding deserts: grasslands are semi-arid regions with extremely fertile soil. If proper soil management is not practiced these are among the most fragile places. Globally desertification of grasslands adjacent to deserts has been a problem.Slide16
Erosion: agricultural lands
on slopes/hills or mountains are very susceptible to water erosion.
Urban
expansion:
has also been a factor in the loss of agricultural land. People have traditionally settled in rich farmland and increasing urbanization is covering up good farmland.
Overgrazing, flooding and
deforestation: have led to the degradation of arable land.Slide17
Read pp. 135-142 (Earth’s Soil Resource)