The 6 Soil Roles A Soil’s role includes: • Serving as a foundation • Emitting and absorbing gases • Providing habitat • Interacting with water • Recycling nutrients • Supporting human settlements
The 5 Factors of Formation Soil is formed by… • Parent Material:the original “Mom & Pop” soil transported from elsewhere, usually by wind or water, at different speeds • Climate: the amount, intensity, timing, and kind of precipitation that breaks down parts of ecosystem (i.e. rocks, trees) into soil • Topography:Slope and Aspect affect the angle of the land and position toward/away from the sun that soil will be exposed to • Biological: Plants, animals, microscopic organisms, and humans interact with soil in different ways • Time: the amount of time it takes for the four factors (above) to interact with each other
What is a Soil Profile? • A Soil Profile is a vertical cross-section of layers of soil found in a given area. Below are two examples of soil profiles.
What is a Soil Horizon? • Soil horizons are the layers in a soil profile used to classify soil types. • Horizons based on color, texture, roots, structure, rock fragments, and any unique characteristic worth noting. • Master Soil Horizons are depicted by a capital letter in the order (from top down): O, A, E, B, C, and R
O-Horizon The “Organic Matter” Horizon • Surface-layer, at depths of 0-2 feet • Dark in color, soft in texture • Humus - rich organic material of plant and animal origin in a stage of decomposition • Leaf litter – leaves, needles, twigs, moss, lichens that are not decomposing • Several O-layers can occur in some soils, consisting only of O-horizons
A-Horizon “Topsoil” or “Biomantle” Horizon • Topmost layer of mineral soil, at depths of 2-10 feet • Some humus present, darker in color than layers below • Biomantle - most biological productive layer; earthworms, fungi, and bacteria live this layer • Smallest and finest soil particles
E-Horizon The “Leaching Layer” Horizon • Small layer between A & B horizons • At depths of 10-15 feet • Light in color, mainly sand & silt • Poor mineral and clay content due to leaching – the loss of water-retaining plant nutrients to the water table • Soil particles larger than in A horizon but smaller than in B horizon
B-Horizon The “Subsoil” Horizon • At depths of 10-30 feet • Rich in clay and minerals like Fe & Al • Some organic material may reach here through leaching • Plant roots can extend into this layer • Red/brown in color due to oxides of Fe & clay
C-Horizon The “Regolith” Horizon • At depths of 30-48 feet • Made up of large rocks or lumps of partially broken bedrock • Least affected by weathering and have changed the least since their origin • Devoid of organic matter due to it being so far down in the soil profile
R-Horizon The “Bedrock” Horizon • At depths of 48+ feet • Deepest soil horizon in the soil profile • No rocks or boulders, only a continuous mass of bedrock • Colors are those of the original rock of the area
How to Make a Soil Profile Ingredients List Directions • 3-4 copies of Master Soil Horizons Worksheet • 30 sticky notes per group (7 per person) • 3-4 pairs of gloves • 1 large glass bowl • 1 one-cup measuring cup • 1 whisk • 1 spatula • 3.5 cups skim milk • 2 packages vanilla Instant Jell-o pudding mix • 1 tiny Ziploc bag Coconut w/green food coloring + raisins • 1 small Ziploc bag crushed chocolate graham crackers & frosting • 1 medium Ziploc bag Chocolate chip & Vanilla wafers & gummy worms • 1 small Ziploc bag crushed Vanilla wafers only • 1 medium Ziploc bag crushed graham crackers • 1 large Ziploc bag crushed Oreo cookies • 1 large Ziploc bag crushed chocolate chips • In large glass bowl, whisk 3.5 cups milk with 2 pkgs. vanilla Instant Jell-o pudding mix until smooth. Let stand 5 minutes. • While waiting, refer to your version of “The Soil Profile” powerpoint to review order that horizons should be. You have A, E, B, R, O, C, and vegetation as horizons. It’s up to you to order it! • After 5 minutes, use spatula to scoop pudding in middle of bowl, allowing for the “dry ingredients” (the bags of various crushed up cookies) to encircle the pudding along the sides of the glass bowl. This creates a vertical cross-section of soil layers visible to you. • Use sticky notes to label each horizon on outside of bowl. • Fill out Master Soil Horizons Worksheet using observations of Soil Profile Dessert. • Turn in worksheet to teacher. Only until you and your team members turn in their worksheet can you enjoy the delicious snack. You’re finished!