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?