soil is a loose mixture of small mineral fragments, organic material, water, and air that can...
TRANSCRIPT
FROM BEDROCK TO SOIL
WHAT IS SOIL?
Soil is a loose mixture of small mineral fragments, organic material, water, and air that can support the growth of vegetation.
ALL SOIL IS DIFFERENT Soil (weathered rock fragments) can be
made of many different types of rock. The type of rock that the soil was made from is called parent rock.
BEDROCK Bedrock is the layer of rock beneath
the soil. Some soil is made from bedrock, so it
remains above the parent rock.
SOIL HORIZONS
Soil is usually layered with humus-rich soil on top, sediment below that, and bedrock on bottom.
HUMUS
Humus is the dark, organic material in soil that is formed from decayed remains of plants and animals.
AIR & WATER
Air must be present in soil to allow water to flow and roots to grow.
Water is essential in dissolving the minerals present in the rock material and distributing it to plant roots.
LEACHING
Leaching is the removal of nutrients that can be dissolved from rock or layers of soil due to the passing of water.
PROPERTIES OF SOIL
Soil texture Soil structure Soil moisture Aeration Soil fertility
SOIL TEXTURE Soil texture is defined as the quality
that is based on the proportions, or size, of the particles. What is its consistency?
Soil texture can influence infiltration of water
SOIL STRUCTURE Soil structure is defined as the
arrangement of soil particles. (not always spread out evenly)
Can determine infiltration Sand, less than 2mm in size Silt, less than .05mm, but more
than .002mm Clay, less than .002mm in size
SOIL FERTILITY
Soil fertility is the ability for soil to hold nutrients and to supply nutrients to a plant.
Which looks like it had the fertile soil?
FERTILITY CAN BE DETERMINED BY
Soil color Soil temperature Soil moisture Humus content
SOIL COLOR Dark brown or back: contain high levels
of humus, very fertile Reddish or Yellowish: contain oxidized
iron, also fertile Whitish: usually contain salt, unsuitable
for farming
SOIL TEMPERATURE & MOISTURE Plant growth is slowed if soil
temperature is too high or too low. The water that is held in the spaces
between soil particles is soil moisture Amount of moisture in soil determines
if water to infiltration or cause run-off
SOIL TYPES AND CLIMATE
DESERT CLIMATES Less than 25cm precipitation per year,
so leaching not a problem Low rate of chemical weathering means
slow soil formation & no mineral distribution
Less ability to support plants or animals High concentration of salt from
evaporation
TROPICAL RAINFOREST CLIMATE Air is very humid and land received
large amounts of water Temperatures are warm year round
allowing rapid decomposition, forming rich humus
Topsoil is thin, and nutrient poor due to leaching and high demand for nutrients from lush plant life
TEMPERATE FOREST & GRASSLAND CLIMATES
Right balance of moisture and temperature
Changes in temperature results in frost action
Thick, very fertile soil develops Very productive for farming
ARCTIC CLIMATES Like cold deserts Extreme low temperature, low
precipitation Little plant or animal life Low decomposition rate, limits humus Little chemical weathering, so slow soil
formation
SO….
What is the source of soil, and how do they differ?
How do climates affect soil formation?
SOIL DESTRUCTION
EROSION
Erosion is the process by which wind, water, gravity, or ice transport soil and sediment from one location to another.
Soil unprotected by plant growth can be lost.
SALINIZATION
The accumulation of salts in soil is know as salinization.
Common to parts of the world where rainfall is low.
DEFORESTATION
Clearing of trees from and area without replacing them is deforestation.
Leaves soil exposed to erosion.
LAND DEGRADATION
When soil is overused it loses its nutrients it is called land degradation. This can happen from poor farming
techniques, over mining, cutting trees or overgrazing.
DESERTIFICATION
Desertification is a process where land becomes more desert-like as a result of change in climate, prolonged drought, or human activity.
SOIL CONSERVATION
Soil Conservation is a method to maintain the fertility of soil by preventing erosion and the loss of nutrients.
SOIL CONSERVATION
There are many ways that farmers help prevent erosion. We will focus on the physical measures. Contour plowing Terracing No-till farming Cover crops Crop rotation
CONTOUR PLOWING
Plowing across the slope of hills to prevent erosion.
TERRACING
Changing one steep field into a series of small, flat fields.
NO-TILL FARMING
No-till farming is a method of farming where the farmer harvests his crops without turning over the soil.
COVER CROPS
Cover crops are crops that are planted between harvests to replace certain nutrients in the soil and prevent erosion.
CROP ROTATION
Rotating crops from one year to the next in order to slow down nutrient depletion. And reduce insect damage to crops.
SO…
How does soil quality affect us? How can we show good stewardship?