Soil: “No soil, NO planet Earth” Mr R & Ms G Soil: “No soil, NO planet Earth” Soil involves numerous connections with physical, chemical and biological processes. For thousands of years soil has been a perfect example of how humans interact and need the Earth to survive. Agriculture, cultivation and farming have all existed because of soils. The ability to understand and investigate soil has led to population growth and feeding the world’s population in areas of the planet with decreased fertility.

Soil Terminology Soil profile – the view of all layers/horizons in the soil. The profile contains the O, A, B, C and Bedrock layers. Shows the thickness of soil, color and chemical composition of soil and relative age (mature or immature) of the soil. Soil Horizon – layers or zones of soil. Separated by different colors, textures, and structure. O, A, B, C and R (parent rock/bedrock) Top soil – A combination of the O and A horizon. Valuable assets for growth of plants and agriculture. Contains organic material, humus (dead or decaying material) and habitats fro animals.

Soil Terminology Organic matter: part of the O and A horizon Living material Root system Provides nutrients and chemicals to and from the soil Sub soil: B Horizon less organic material present Limit of borrowing animals - Zone of accumulation (nutrients and leeching) Soil particles: -soil is made of 3 main particles – SAND, SILT and CLAY. These are characterized by their particle size and absorption of different chemicals.

Soil Terminology Humus – dead or decaying matter. Located in the O and A horizon Parent material – A layer of rock which is the beginning of the soil formation process. This rock layer would be changed and broken down by physical and chemical weathering to create weathered material. (C horizon) Bedrock – a layer of rock which is beneath the soil horizons and produces a natural barrier for percolating water (groundwater) and a base for the formation of soil. Weathered material – material which comes from the parent rock or bed rock. This is broken down by physical and chemical weathering over a long period of time.

Soil Composition

Soil Formation https://www.youtube.com/watch?v=7iyxocIhfu0

Soil Formation - Factors Plants & Animals Contains organic matter Recycling of nutrients Bacteria (nitrogen cycle) Creates soil fertility Slope Surface runoff Leeching and percolation rates Parent Material Develops from parent material Undergoes physical and chemical weathering to change the rock into soil Time Takes time to weathering and change the soil Longer time – thicker more developed soil Climate temperature and precipitation Develops different types of soil Amount of leeching

Soil Profile The soil profile is the different zones or layers starting at the surface and moving vertically down to the bedrock or parent rock Top soil is made up of two distinct layers/zones – O horizon and A horizon. O horizon: consists of the first 2 inches of soil. Organic material (plant litter, animals) A horizon: Mixture of minerals, organic matter and humus

Soil Profile Subsoil contains the following: B Horizon: Zone of fine clay – brought down from the A horizon Some biological roots – this is the lowest point of tree roots Zone of accumulation – shown by the color. Bright colors represent more movement of minerals from the top soil. Little humus or organic matter Above the C horizon

C horizon: Contains parent material Larger rocks and sediments Mostly regolith – not soil Clear difference between the B and C horizon – color and composition First layer to be developed from the underlying bedrock or parent material.

Soil Texture Soil consists of 3 parts: Sand – 0.05-2mm Different levels of sand between fine and coarse. Silt – 0.002-0.05mm diameter Helps move water through the soil Clay – Less than 0.002mm in diameter smallest particle size Loam – an ideal mixture of sand, silt and clay create an ideal and fertile soil