Air is the breath of life, Water is the drink of life, Soil is the food of life.

• “To be a successful farmer one must first know the nature of the soil.” - Xenophon, Oeconomicus, 400 B.C.

• “We know more about the movement of stars and planets than about the soil underfoot.”

- Leonardo Da Vinci, 1500’s

• “We are part of the earth and it is part of us ... What befalls the earth befalls all the sons of the earth”

- Chief Seattle, 1852

• "The love of dirt is among the earliest of passions, as it is the latest. Mud-pies gratify one of our first and best instincts. So long as we are dirty, we are pure. Fondness for the ground comes back to a man after he has run the round of pleasure and business, eaten dirt, and sown wild oats, drifted about the world, and taken the wind of all its moods. The love of digging in the ground (or of looking on while he pays another to dig) is as sure to come back to him, as he is sure, at last, to go under the ground, and stay there.“

- Charles Dudley Warner, My Summer in a Garden, 1870

• "Soil is a resource, a living, breathing entity that, if treated properly, will maintain itself. It's our lifeline for survival. When it has finally been depleted, the human population will disappear. .... Project your imagination into the soil below you next time you go into the garden. Think with compassion of the life that exists there. Think, the drama, the sexuality, the harvesting, the work that carries on ceaselessly. Think about the meaning of being a steward for the earth."- Marjorie Harris, In the Garden, 1995

"If we do not permit the Earth to producebeauty and joy, it will in the end not produce food either."

- Joseph Wood Krutch

"A nation that destroys its soils destroys itself." - President Franklin D. Roosevelt

Soil is both abiotic and biotic

• Essentially a mixture of • 50% porous spaces• 45% pulverized rock• 5% organic matter

• It rests on a bed of rock, bedrock (the parent material of the abiotic portion)

• Soil formation is a long slow process. • It's estimated that 3 cm of soil takes

500 to 1000 years to form!

• Soil is constantly being formed. • It is also constantly being eroded.

Erosion – the movement of soil from one place to another.

Functions of Soil

How is soil made?

Mechanical WeatheringSoil begins when rocks are broken down into smaller particles by natural forces (e.g. wind, water, ice).

Chemical WeatheringChemicals – that are part of the rock, in water (acid rain), or even oxygen in the air further the erosion process, and change the chemical composition of the soil.

4Fe+2 +3O2 --> 2Fe2O3

IRON + OXYG RUST

Limestone (rain)

Weathering by salt crystals

Biological Weathering

• Plants, animals, microorganisms assist in either mechanical or chemical weathering

Lichen (releases acids)

Action of Mollusks

Tree Roots

Soil Horizons• O Organic material: leaf litter

(undecomposed) (DETRITUS)

• A Topsoil (Surface soil) Minerals and humus (formed from decomposition of plants and leaves) - most organic matter and soil life in this layer

• B Subsoil – accumulation of clay and organic materials

• C Unweathered bedrock (parent rock) A Soil Pedon

Soil Organic Matter• O Organic material: leaf

litter (not yet decomposed)

• A Topsoil - humus (formed from decomposition of plants and leaves) - most organic matter and soil life in this layer

- Organic matter enhances water and nutrient holding capacity and improves soil structure- Humus is usually dark and is the “glue” that helps hold soil particles together

Earthworm excrement!Also called “castings”

Colour of Soils

• Usually indicates its mineral composition and sometimes its fertility

• E.g. red soils = high iron content (P.E.I.)• E.g. dark brown/black soils – rich in organics• E.g. gray/white soils – low organic content

• Before soil testing was possible, the colour was often used by farmers/ranchers to indicate suitability for crops or grazing

Soil Texture

• 3 Types of soil particle classified by size• Sand: 1 – 5 mm diameter• Silt: 0.1 mm – 1.0 mm• Clay: 0.001 mm – 0.1 mm

• Soils are named depending on the relative quantities of these particles (e.g. silty clay, sandy clay etc.)

• Mineral components of soil (e.g. Fe, Mg, Ca, K ….)• Biotic components of soil (fungi, invertebrates, roots ….)

The Soil Triangle - Textural Class

EXAMPLE:10% SAND40% CLAY50% SILT

The soil type therefore isSILTY CLAY

EXAMPLE:40% SAND20% CLAY40% SILT

The soil type therefore isMEDIUM LOAM

Why does this matter?

• The texture of soil will determine the rate at which water can infiltrate the soil.

• For example, sand particles are large – therefore the spaces between them will be large. Water will flow through pure sand very quickly!

• Also the texture will determine how much water can be stored in the soil (for plants to draw from during dry spells).

LOAM• The best soil for agricultural purposes

• It is a rich soil consisting of a mixture of sand, silt and clay (approx. 40:40:20 ratio), and usually decaying organic material called humus

Soil and Agriculture

• For a farmer, the soil texture influences its workability (ease of cultivation)

• Texture influences two important qualities:• 1. Permeability – the rate at which water can

flow through the soil• 2. Porosity – the amount of volume of spaces

between soil particles (pores can be filled with water or air)

Which has the greater pore space (porosity)? Which soil can hold more water/air?Which soil will allow water to flow more freely into it?

Soil and water movement

• http://www.youtube.com/watch?v=LDf2sYxwAOg&feature=endscreen&NR=1

• Shape of particles will also determine rate of water flow.

Soil Fauna (Animal Life)

• An incredible diversity of organisms live in the soil (microscopic and visible)

• Organisms live in microscale environments within and between soil particles. Differences over short distances in pH, moisture, pore size, and the types of food available create a broad range of habitats.

• Earthworms, spiders, centipedes, beetles• Bacteria, protozoans

Soil Organisms - Benefits1. Decomposition of dead plants/animals2. Infiltration and storage of water

- larger organisms create channels and aggregates (clumps of material) - this increases the rate of water flow through the soil

3. Recycling of nutrients - example: conversion of organic nitrogen (in

proteins, amino acids) into nitrates which plants can then use again (bacterial decomposers)

Soils have a Food Web too!• All plants depend on the soil food web for

their nutrition (via decomposition)

• Soil Organisms tend to live in the top few centimeters of the soil horizon.

Example: Mites

Example: Nematodes

Soil Microbes (single cell creatures)

When are they most active?

Late Spring – Mid Fall

Capturing Soil Organisms using a Berlese Funnel

Soil Testing – next Monday• Bring 2 – 3 cups of soil (as dry as possible) that you

have taken from the ground (NOT POTTING SOIL OR “TRIPLE MIX” FROM A BAG!!!!) – in a sealed bag

• Porosity• Permeability• Water Holding Capacity• Bulk Density• pH• Presence of some ions (e.g. Nitrate)• Soil Biodiversity (Berlese Funnel)